From 6cbecb5b397730af25ff2453c90180917a160727 Mon Sep 17 00:00:00 2001
From: Sebastian Serth <Sebastian.Serth@hpi.de>
Date: Fri, 14 May 2021 10:51:44 +0200
Subject: [PATCH] Apply automatic rubocop fixes

---
 Rakefile                                      |   4 +-
 Vagrantfile                                   |   6 +-
 app/channels/application_cable/channel.rb     |   2 +
 app/channels/application_cable/connection.rb  |   8 +-
 app/channels/la_exercises_channel.rb          |   4 +-
 app/controllers/admin/dashboard_controller.rb |   2 +
 app/controllers/application_controller.rb     |   5 +-
 .../code_ocean/files_controller.rb            |  12 +-
 .../codeharbor_links_controller.rb            |   3 +-
 app/controllers/comments_controller.rb        |  32 +-
 app/controllers/concerns/common_behavior.rb   |   8 +-
 app/controllers/concerns/file_parameters.rb   |   3 +-
 app/controllers/concerns/lti.rb               |  52 ++-
 .../concerns/remote_evaluation_parameters.rb  |   9 +-
 .../concerns/submission_parameters.rb         |   7 +-
 .../concerns/submission_scoring.rb            |  17 +-
 app/controllers/consumers_controller.rb       |   8 +-
 .../error_template_attributes_controller.rb   |  37 +-
 app/controllers/error_templates_controller.rb |  22 +-
 .../execution_environments_controller.rb      |  41 +-
 .../exercise_collections_controller.rb        |  31 +-
 app/controllers/exercises_controller.rb       |  74 ++--
 app/controllers/external_users_controller.rb  |  24 +-
 app/controllers/file_templates_controller.rb  |  23 +-
 app/controllers/file_types_controller.rb      |  18 +-
 app/controllers/flowr_controller.rb           |  11 +-
 app/controllers/internal_users_controller.rb  |   3 +-
 app/controllers/proxy_exercises_controller.rb |  28 +-
 .../remote_evaluation_controller.rb           |  12 +-
 .../request_for_comments_controller.rb        |  61 +--
 app/controllers/sessions_controller.rb        |   9 +-
 app/controllers/statistics_controller.rb      |  26 +-
 app/controllers/study_groups_controller.rb    |   8 +-
 app/controllers/submissions_controller.rb     | 226 +++++-----
 app/controllers/subscriptions_controller.rb   |  44 +-
 app/controllers/tags_controller.rb            |   8 +-
 app/controllers/tips_controller.rb            |  12 +-
 .../user_exercise_feedbacks_controller.rb     |  26 +-
 app/helpers/action_cable_helper.rb            |  19 +-
 app/helpers/admin/dashboard_helper.rb         |   2 +
 app/helpers/application_helper.rb             |  25 +-
 .../error_template_attributes_helper.rb       |   2 +
 app/helpers/error_templates_helper.rb         |   2 +
 app/helpers/exercise_helper.rb                |   6 +-
 app/helpers/lti_helper.rb                     |   2 +
 app/helpers/pagedown_form_builder.rb          |  13 +-
 app/helpers/statistics_helper.rb              | 371 ++++++++--------
 app/helpers/time_helper.rb                    |   6 +-
 app/mailers/user_mailer.rb                    |  22 +-
 app/models/anomaly_notification.rb            |   2 +
 app/models/code_ocean/file.rb                 |  31 +-
 app/models/codeharbor_link.rb                 |   6 +-
 app/models/concerns/context.rb                |   2 +
 app/models/concerns/creation.rb               |   2 +
 app/models/concerns/default_values.rb         |   2 +
 app/models/consumer.rb                        |   2 +
 app/models/error_template.rb                  |   2 +
 app/models/error_template_attribute.rb        |   2 +
 app/models/event.rb                           |   2 +
 app/models/execution_environment.rb           |  17 +-
 app/models/exercise.rb                        |  80 ++--
 app/models/exercise_collection.rb             |  13 +-
 app/models/exercise_collection_item.rb        |   2 +
 app/models/exercise_tag.rb                    |  11 +-
 app/models/exercise_tip.rb                    |   8 +-
 app/models/external_user.rb                   |   9 +-
 app/models/file_template.rb                   |   5 +-
 app/models/file_type.rb                       |  12 +-
 app/models/internal_user.rb                   |   4 +-
 app/models/intervention.rb                    |   8 +-
 app/models/lti_parameter.rb                   |  14 +-
 app/models/proxy_exercise.rb                  | 411 +++++++++---------
 app/models/request_for_comment.rb             |   4 +-
 app/models/search.rb                          |   4 +-
 app/models/structured_error.rb                |   8 +-
 app/models/structured_error_attribute.rb      |  11 +-
 app/models/study_group_membership.rb          |   2 +-
 app/models/submission.rb                      |  34 +-
 app/models/subscription.rb                    |   2 +
 app/models/tag.rb                             |  12 +-
 app/models/testrun.rb                         |   6 +-
 app/models/tip.rb                             |   9 +-
 app/models/user.rb                            |   7 +-
 app/models/user_exercise_feedback.rb          |   8 +-
 app/models/user_exercise_intervention.rb      |   6 +-
 app/models/user_proxy_exercise_exercise.rb    |   8 +-
 app/policies/admin/dashboard_policy.rb        |   2 +
 app/policies/admin_only_policy.rb             |   4 +-
 app/policies/admin_or_author_policy.rb        |   6 +-
 app/policies/application_policy.rb            |   8 +-
 app/policies/code_ocean/file_policy.rb        |   4 +-
 app/policies/codeharbor_link_policy.rb        |   2 +
 app/policies/comment_policy.rb                |   4 +-
 app/policies/consumer_policy.rb               |   3 +-
 .../error_template_attribute_policy.rb        |   3 +-
 app/policies/error_template_policy.rb         |   2 +
 app/policies/event_policy.rb                  |   4 +-
 app/policies/execution_environment_policy.rb  |   4 +-
 app/policies/exercise_collection_policy.rb    |   4 +-
 app/policies/external_user_policy.rb          |   2 +
 app/policies/file_template_policy.rb          |   4 +-
 app/policies/file_type_policy.rb              |   3 +-
 app/policies/internal_user_policy.rb          |   2 +
 app/policies/proxy_exercise_policy.rb         |   6 +-
 app/policies/search_policy.rb                 |   6 +-
 app/policies/statistics_policy.rb             |   6 +-
 app/policies/study_group_policy.rb            |   4 +-
 app/policies/submission_policy.rb             |   6 +-
 app/policies/subscription_policy.rb           |   2 +
 app/policies/tag_policy.rb                    |   4 +-
 app/policies/tip_policy.rb                    |   4 +-
 app/policies/user_exercise_feedback_policy.rb |   4 +-
 .../exercise_service/check_external.rb        |   5 +-
 .../exercise_service/push_external.rb         |   2 +-
 .../convert_exercise_to_task.rb               |  26 +-
 .../convert_task_to_exercise.rb               |   8 +-
 app/services/proforma_service/import.rb       |   4 +-
 app/uploaders/file_uploader.rb                |   2 +
 app/views/code_ocean/files/show.json.jbuilder |   2 +
 app/views/comments/index.json.jbuilder        |   2 +
 app/views/comments/show.json.jbuilder         |   2 +
 app/views/exercises/reload.json.jbuilder      |   2 +
 app/views/file_types/show.json.jbuilder       |   2 +
 .../proxy_exercises/reload.json.jbuilder      |   2 +
 .../request_for_comments/index.json.jbuilder  |   2 +
 .../request_for_comments/show.json.jbuilder   |   2 +
 app/views/submissions/show.json.jbuilder      |   5 +-
 config.ru                                     |   4 +-
 config/application.rb                         |   6 +-
 config/boot.rb                                |   2 +
 config/environment.rb                         |   2 +
 config/environments/development.rb            |   4 +-
 config/environments/production.rb             |   2 +-
 config/environments/test.rb                   |   4 +-
 .../application_controller_renderer.rb        |   1 +
 config/initializers/assets.rb                 |   2 +-
 config/initializers/backtrace_silencers.rb    |   4 +-
 config/initializers/cookies_serializer.rb     |   2 +
 .../initializers/filter_parameter_logging.rb  |   6 +-
 config/initializers/inflections.rb            |   1 -
 config/initializers/mime_types.rb             |   1 +
 config/initializers/monkey_patches.rb         |   6 +-
 config/initializers/permissions_policy.rb     |   1 +
 config/initializers/prometheus.rb             |   2 +-
 config/initializers/rails_admin.rb            |  11 +-
 config/initializers/session_store.rb          |   2 +
 config/initializers/sorcery.rb                |  56 +--
 config/initializers/will_paginate.rb          |   2 +
 config/initializers/wrap_parameters.rb        |   2 +
 config/puma.rb                                |  14 +-
 config/schedule.rb                            |   4 +-
 config/spring.rb                              |  10 +-
 db/migrate/20140625134118_create_exercises.rb |   2 +
 ...626143132_create_execution_environments.rb |   2 +
 .../20140626144036_create_submissions.rb      |   2 +
 ...d_reference_implementation_to_exercises.rb |   2 +
 ...d_indent_size_to_execution_environments.rb |   2 +
 db/migrate/20140701120126_create_consumers.rb |   2 +
 db/migrate/20140701122345_create_users.rb     |   2 +
 ...140702100130_add_oauth_key_to_consumers.rb |   2 +
 ...703070749_add_oauth_secret_to_consumers.rb |   2 +
 .../20140716153147_add_role_to_users.rb       |   2 +
 ...20140717074902_add_user_id_to_exercises.rb |   2 +
 ...d_run_command_to_execution_environments.rb |   2 +
 ..._test_command_to_execution_environments.rb |   2 +
 ...140723135747_add_test_code_to_exercises.rb |   2 +
 ...20140724155359_add_cause_to_submissions.rb |   2 +
 ...343_add_template_test_code_to_exercises.rb |   2 +
 ...upports_user_defined_tests_to_exercises.rb |   2 +
 ...ing_framework_to_execution_environments.rb |   2 +
 .../20140812102114_create_file_types.rb       |   2 +
 db/migrate/20140812144733_create_files.rb     |   2 +
 ...ted_columns_from_execution_environments.rb |   2 +
 ...ove_file_related_columns_from_exercises.rb |   2 +
 ...0813091722_remove_code_from_submissions.rb |   2 +
 ...820170039_add_instructions_to_exercises.rb |   2 +
 ...140821064318_add_published_to_exercises.rb |   2 +
 ...0823172643_add_executable_to_file_types.rb |   2 +
 ...0823173923_add_renderable_to_file_types.rb |   2 +
 .../20140825121336_create_external_users.rb   |   2 +
 .../20140825125801_create_internal_users.rb   |   2 +
 db/migrate/20140825154202_drop_users.rb       |   2 +
 ...140825161350_add_user_type_to_exercises.rb |   2 +
 ...40825161358_add_user_type_to_file_types.rb |   2 +
 ...0825161406_add_user_type_to_submissions.rb |   2 +
 db/migrate/20140826073318_sorcery_core.rb     |   2 +
 ...26073319_sorcery_brute_force_protection.rb |   2 +
 .../20140826073320_sorcery_remember_me.rb     |   2 +
 .../20140826073321_sorcery_reset_password.rb  |   2 +
 .../20140826073322_sorcery_user_activation.rb |   2 +
 ...20140827065359_add_binary_to_file_types.rb |   2 +
 ...20140827083957_add_native_file_to_files.rb |   2 +
 db/migrate/20140829141913_create_hints.rb     |   2 +
 ...ot_null_constraints_from_internal_users.rb |   2 +
 db/migrate/20140903165113_create_errors.rb    |   2 +
 .../20140904082810_add_token_to_exercises.rb  |   2 +
 ...20140909115430_add_file_id_to_exercises.rb |   2 +
 .../20140915095420_add_role_to_files.rb       |   2 +
 ...915122846_remove_file_id_from_exercises.rb |   2 +
 ...40918063522_add_hashed_content_to_files.rb |   2 +
 ...922161120_add_feedback_message_to_files.rb |   2 +
 .../20140922161226_add_weight_to_files.rb     |   2 +
 ...2729_add_help_to_execution_environments.rb |   2 +
 ...exposed_ports_to_execution_environments.rb |   2 +
 ...xecution_time_to_execution_environments.rb |   2 +
 ...and_user_type_to_execution_environments.rb |   2 +
 ...141017110211_rename_published_to_public.rb |   2 +
 .../20141031161603_add_path_to_files.rb       |   2 +
 db/migrate/20141119131607_create_comments.rb  |   2 +
 db/migrate/20150128083123_create_teams.rb     |   2 +
 ...50128084834_create_internal_users_teams.rb |   2 +
 ...20150128093003_add_team_id_to_exercises.rb |   2 +
 ...add_pool_size_to_execution_environments.rb |   2 +
 ..._file_type_id_to_execution_environments.rb |   2 +
 ..._memory_limit_to_execution_environments.rb |   2 +
 ...twork_enabled_to_execution_environments.rb |   2 +
 ...50327141740_create_request_for_comments.rb |   8 +-
 .../20150408155923_add_submission_to_error.rb |   2 +
 .../20150421074734_add_file_index_to_files.rb |   4 +-
 ...4_add_user_type_to_request_for_comments.rb |   2 +
 .../20150818142251_correct_column_names.rb    |   8 +-
 ...ove_requestor_from_request_for_comments.rb |   2 +
 ...2125415_add_hide_file_tree_to_exercises.rb |   2 +
 ...20160204094409_create_code_harbor_links.rb |   2 +
 ...0204111716_add_user_to_code_harbor_link.rb |   4 +-
 db/migrate/20160302133540_create_testruns.rb  |   2 +
 ...51_add_question_to_request_for_comments.rb |   2 +
 ...41_add_allow_file_creation_to_exercises.rb |   2 +
 ...comment_text_attribute_to_text_datatype.rb |   3 +
 .../20160609185708_create_file_templates.rb   |   2 +
 ...0160610111602_add_file_template_to_file.rb |   2 +
 ...0951_add_solved_to_request_for_comments.rb |   2 +
 ..._add_submission_to_request_for_comments.rb |  54 +--
 ..._requested_at_from_request_for_comments.rb |   2 +
 db/migrate/20160704143402_remove_teams.rb     |   2 +
 ..._add_allow_auto_completion_to_exercises.rb |   2 +
 .../20170112151637_create_lti_parameters.rb   |   4 +-
 ...70437_create_remote_evaluation_mappings.rb |  14 +-
 ...70205163247_create_exercise_collections.rb |   3 +-
 .../20170205165450_create_proxy_exercises.rb  |   2 +
 .../20170205210357_create_interventions.rb    |   5 +-
 db/migrate/20170206141210_add_tags.rb         |   4 +-
 .../20170206152503_add_user_feedback.rb       |   2 +
 db/migrate/20170228165741_add_search.rb       |   2 +
 ..._reason_to_user_proxy_exercise_exercise.rb |   2 +
 ...20170323130756_add_index_to_submissions.rb |   2 +
 ..._default_for_request_for_comment_solved.rb |   4 +-
 .../20170411090543_improve_user_feedback.rb   |   2 +
 ..._thank_you_note_to_request_for_comments.rb |   2 +
 .../20170703075832_create_error_templates.rb  |   2 +
 ...075959_create_error_template_attributes.rb |   2 +
 ...20170703080205_create_structured_errors.rb |   2 +
 ...0355_create_structured_error_attributes.rb |   2 +
 ..._description_and_hint_to_error_template.rb |   2 +
 ...mplate_attribute_relationship_to_n_to_m.rb |   2 +
 ...add_match_to_structured_error_attribute.rb |   2 +
 .../20170830083601_add_cause_to_testruns.rb   |   8 +-
 .../20170906124500_create_subscriptions.rb    |   2 +
 ...20170913054203_rename_subscription_type.rb |   2 +
 ...70920145852_add_deleted_to_subscription.rb |   2 +
 ...1002131135_remove_expected_working_time.rb |   2 +
 ...y_detection_flag_to_exercise_collection.rb |   4 +-
 ...d_timestamps_to_user_exercise_feedbacks.rb |   6 +-
 .../20171122124222_add_index_to_exercises.rb  |   2 +
 ...0172208_add_user_to_exercise_collection.rb |   4 +-
 ...645_add_submission_to_structured_errors.rb |   2 +
 ...ached_full_score_to_request_for_comment.rb |   8 +-
 ..._times_featured_to_request_for_comments.rb |   2 +
 ...180222145909_fix_timestamps_on_feedback.rb |   6 +-
 ...0226131340_create_anomaly_notifications.rb |   2 +
 ...0_remove_file_id_from_structured_errors.rb |   2 +
 ...125302_create_exercise_collection_items.rb |   2 +
 db/migrate/20180814145059_create_events.rb    |   2 +
 ...14154055_rename_events_type_to_category.rb |   2 +
 .../20180815115351_remove_event_indices.rb    |   4 +-
 ...317_add_index_for_testrun_submission_id.rb |   2 +
 ...dex_for_lti_parameters_external_user_id.rb |   2 +
 ...181116143743_add_role_to_external_users.rb |   2 +
 ...181119161514_add_user_to_proxy_exercise.rb |   4 +-
 .../20181122084546_create_study_groups.rb     |   5 +-
 ...22090243_create_study_group_memberships.rb |   2 +
 ...122090244_add_study_group_to_submission.rb |   2 +
 ...user_type_to_remote_evaluation_mappings.rb |   2 +
 db/migrate/20181127160857_drop_hints.rb       |   2 +
 db/migrate/20181129093207_drop_errors.rb      |  12 +-
 ...02_add_indices_for_request_for_comments.rb |   2 +
 ...e_code_harbor_links_to_codeharbor_links.rb |   2 +
 ..._rename_oauth2token_in_codeharbor_links.rb |   2 +
 .../20190830142809_add_uuid_to_exercise.rb    |   2 +
 ...91008163045_add_unpublished_to_exercise.rb |   2 +
 ...dd_container_execution_time_to_testruns.rb |   2 +
 ...0200506093054_add_deadline_to_exercises.rb |   2 +
 ...nd_submission_to_user_exercise_feedback.rb |   8 +-
 .../20201026184633_create_linter_checks.rb    |   2 +
 db/migrate/20201208095929_add_index_to_rfc.rb |   4 +-
 ...2844_add_index_to_unpublished_exercises.rb |   2 +
 ...01210113500_add_index_to_exercise_title.rb |   2 +
 ..._to_active_storage_blobs.active_storage.rb |  16 +-
 ..._storage_variant_records.active_storage.rb |   4 +-
 db/seeds.rb                                   |   4 +-
 db/seeds/audio_video/index.html_spec.rb       |   2 +
 db/seeds/development.rb                       |   2 +-
 db/seeds/fibonacci/exercise.rb                |   5 +-
 db/seeds/fibonacci/exercise_spec_1.rb         |   2 +
 db/seeds/fibonacci/exercise_spec_2.rb         |   4 +-
 db/seeds/fibonacci/exercise_spec_3.rb         |   2 +
 db/seeds/fibonacci/reference.rb               |   2 +
 db/seeds/files/exercise.rb                    |   2 +
 db/seeds/files/exercise_spec.rb               |   2 +
 db/seeds/hello_world/exercise_spec.rb         |   2 +
 db/seeds/production.rb                        |   4 +-
 db/seeds/sql_select/comparator.rb             |   2 +
 db/seeds/tdd/exercise_spec.rb                 |   2 +
 db/seeds/web_app/app.rb                       |   2 +
 .../validations/boolean_presence_validator.rb |   2 +
 lib/assessor.rb                               |  10 +-
 lib/code_ocean/config.rb                      |   6 +-
 lib/cpp_catch2_adapter.rb                     |  44 +-
 lib/docker_client.rb                          | 164 +++----
 lib/docker_container_mixin.rb                 |  11 +-
 lib/docker_container_pool.rb                  |  31 +-
 lib/file_tree.rb                              |  16 +-
 .../testing_framework_adapter_generator.rb    |  38 +-
 lib/junit_adapter.rb                          |  10 +-
 lib/mocha_adapter.rb                          |   8 +-
 lib/nonce_store.rb                            |   4 +-
 lib/port_pool.rb                              |   4 +-
 lib/prometheus/controller.rb                  |  22 +-
 lib/py_lint_adapter.rb                        |  19 +-
 lib/py_unit_adapter.rb                        |  14 +-
 lib/py_unit_and_py_lint_adapter.rb            |   3 +-
 lib/python20_course_week.rb                   |  27 +-
 lib/r_script_adapter.rb                       |   6 +-
 lib/rspec_adapter.rb                          |   4 +-
 lib/seeds_helper.rb                           |   2 +
 lib/sql_result_set_comparator_adapter.rb      |   6 +-
 lib/tasks/detect_exercise_anomalies.rake      |  15 +-
 lib/tasks/docker.rake                         |   4 +-
 lib/tasks/write_displaynames.rake             |  14 +-
 lib/testing_framework_adapter.rb              |   4 +-
 spec/concerns/file_parameters_spec.rb         |   2 +-
 spec/concerns/lti_spec.rb                     |  16 +-
 spec/concerns/submission_scoring_spec.rb      |  10 +-
 .../admin/dashboard_controller_spec.rb        |   8 +-
 .../application_controller_spec.rb            |  18 +-
 .../code_ocean/files_controller_spec.rb       |  17 +-
 spec/controllers/consumers_controller_spec.rb |  29 +-
 ...ror_template_attributes_controller_spec.rb |  29 +-
 .../error_templates_controller_spec.rb        |  29 +-
 spec/controllers/events_controller_spec.rb    |  18 +-
 .../execution_environments_controller_spec.rb |  47 +-
 spec/controllers/exercises_controller_spec.rb |  71 +--
 .../external_users_controller_spec.rb         |   9 +-
 .../controllers/file_types_controller_spec.rb |  29 +-
 .../internal_users_controller_spec.rb         |  90 ++--
 .../request_for_comments_controller_spec.rb   |   6 +-
 spec/controllers/sessions_controller_spec.rb  |  61 ++-
 .../controllers/statistics_controller_spec.rb |  18 +-
 .../submissions_controller_spec.rb            |  83 ++--
 spec/factories/code_ocean/file.rb             |   2 +
 spec/factories/codeharbor_link.rb             |   4 +-
 spec/factories/consumer.rb                    |   2 +
 spec/factories/error_template_attributes.rb   |   6 +-
 spec/factories/error_templates.rb             |   6 +-
 spec/factories/execution_environment.rb       |   2 +
 spec/factories/exercise.rb                    |   6 +-
 spec/factories/external_user.rb               |   2 +
 spec/factories/file_type.rb                   |   2 +
 spec/factories/lti_parameter.rb               |  11 +-
 spec/factories/proxy_exercise.rb              |   3 +-
 spec/factories/shared_traits.rb               |   6 +-
 spec/factories/structured_error_attributes.rb |   4 +-
 spec/factories/structured_errors.rb           |   2 +
 spec/factories/study_group.rb                 |   2 +
 spec/factories/submission.rb                  |   2 +
 spec/factories/user_exercise_feedback.rb      |   3 +-
 spec/features/authentication_spec.rb          |   4 +-
 spec/features/authorization_spec.rb           |   9 +-
 spec/features/editor_spec.rb                  |  10 +-
 spec/features/factories_spec.rb               |   2 +
 spec/features/prometheus/controller_spec.rb   |   1 -
 .../request_for_comments_filter_spec.rb       |   2 +
 spec/helpers/admin/dashboard_helper_spec.rb   |   4 +-
 spec/helpers/application_helper_spec.rb       |   2 +
 spec/helpers/exercise_helper_spec.rb          |   2 +
 spec/helpers/yaml_spec.rb                     |   2 +-
 spec/lib/assessor_spec.rb                     |   8 +-
 spec/lib/code_ocean/config_spec.rb            |  12 +-
 spec/lib/docker_client_spec.rb                |  70 +--
 spec/lib/docker_container_mixin_spec.rb       |   2 +
 spec/lib/file_tree_spec.rb                    |   4 +-
 ...esting_framework_adapter_generator_spec.rb |   6 +-
 spec/lib/junit_adapter_spec.rb                |   2 +
 spec/lib/mocha_adapter_spec.rb                |   4 +-
 spec/lib/nonce_store_spec.rb                  |   2 +
 spec/lib/port_pool_spec.rb                    |   2 +
 spec/lib/py_unit_adapter_spec.rb              |   2 +
 spec/lib/rspec_adapter_spec.rb                |   2 +
 .../sql_result_set_comparator_adapter_spec.rb |   2 +
 spec/lib/testing_framework_adapter_spec.rb    |   2 +
 spec/mailers/previews/user_mailer_preview.rb  |   4 +-
 spec/mailers/user_mailer_spec.rb              |   6 +-
 spec/models/code_ocean/file_spec.rb           |   8 +-
 spec/models/codeharbor_link_spec.rb           |   2 +
 spec/models/consumer_spec.rb                  |   2 +
 spec/models/execution_environment_spec.rb     |  15 +-
 spec/models/exercise_spec.rb                  |  19 +-
 spec/models/external_user_spec.rb             |   2 +
 spec/models/file_type_spec.rb                 |   8 +-
 spec/models/internal_user_spec.rb             |   7 +-
 spec/models/submission_spec.rb                |  33 +-
 spec/policies/admin/dashboard_policy_spec.rb  |   2 +
 spec/policies/application_policy_spec.rb      |   2 +
 spec/policies/code_ocean/file_policy_spec.rb  |  10 +-
 spec/policies/consumer_policy_spec.rb         |   6 +-
 .../execution_environment_policy_spec.rb      |  10 +-
 spec/policies/exercise_policy_spec.rb         |  21 +-
 spec/policies/external_user_policy_spec.rb    |   6 +-
 spec/policies/file_type_policy_spec.rb        |   6 +-
 spec/policies/internal_user_policy_spec.rb    |  10 +-
 spec/policies/submission_policy_spec.rb       |   8 +-
 spec/rails_helper.rb                          |   2 +-
 .../convert_exercise_to_task_spec.rb          |   6 +-
 .../convert_task_to_exercise_spec.rb          |  14 +-
 spec/services/proforma_service/import_spec.rb |  12 +-
 spec/spec_helper.rb                           |   6 +-
 spec/support/anonymous_controller.rb          |   5 +-
 spec/support/authentication.rb                |   2 +
 spec/support/controllers.rb                   |  14 +-
 spec/support/database_cleaner.rb              |   1 -
 spec/support/docker.rb                        |   4 +-
 spec/support/expectations/equal_exercise.rb   |   2 +-
 spec/support/factory_bot.rb                   |   2 +
 spec/support/features.rb                      |   2 +
 spec/support/selenium.rb                      |   2 +
 spec/support/silencer.rb                      |   2 +
 spec/support/wait_for_ajax.rb                 |   2 +
 spec/uploaders/file_uploader_spec.rb          |   7 +-
 .../shell.html.slim_spec.rb                   |   4 +-
 .../exercises/implement.html.slim_spec.rb     |   6 +-
 440 files changed, 2705 insertions(+), 1853 deletions(-)

diff --git a/Rakefile b/Rakefile
index ba6b733d..e51cf0e1 100644
--- a/Rakefile
+++ b/Rakefile
@@ -1,6 +1,8 @@
+# frozen_string_literal: true
+
 # Add your own tasks in files placed in lib/tasks ending in .rake,
 # for example lib/tasks/capistrano.rake, and they will automatically be available to Rake.
 
-require File.expand_path('../config/application', __FILE__)
+require File.expand_path('config/application', __dir__)
 
 Rails.application.load_tasks
diff --git a/Vagrantfile b/Vagrantfile
index 8b15904e..b4b9999b 100644
--- a/Vagrantfile
+++ b/Vagrantfile
@@ -10,9 +10,9 @@ Vagrant.configure(2) do |config|
     v.cpus = 4
   end
   config.vm.network 'forwarded_port',
-                    host_ip: ENV['LISTEN_ADDRESS'] || '127.0.0.1',
-                    host: 7000,
-                    guest: 7000
+    host_ip: ENV['LISTEN_ADDRESS'] || '127.0.0.1',
+    host: 7000,
+    guest: 7000
   config.vm.synced_folder '.', '/home/vagrant/codeocean'
   config.vm.synced_folder '../dockercontainerpool', '/home/vagrant/dockercontainerpool'
   config.vm.provision 'shell', path: 'provision/provision.vagrant.sh', privileged: false
diff --git a/app/channels/application_cable/channel.rb b/app/channels/application_cable/channel.rb
index d6726972..9aec2305 100644
--- a/app/channels/application_cable/channel.rb
+++ b/app/channels/application_cable/channel.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ApplicationCable
   class Channel < ActionCable::Channel::Base
   end
diff --git a/app/channels/application_cable/connection.rb b/app/channels/application_cable/connection.rb
index d277ba3e..f2bc6ed9 100644
--- a/app/channels/application_cable/connection.rb
+++ b/app/channels/application_cable/connection.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ApplicationCable
   class Connection < ActionCable::Connection::Base
     identified_by :current_user
@@ -20,11 +22,7 @@ module ApplicationCable
     def find_verified_user
       # Finding the current_user is similar to the code used in application_controller.rb#current_user
       current_user = ExternalUser.find_by(id: session[:external_user_id]) || InternalUser.find_by(id: session[:user_id])
-      if current_user
-        current_user
-      else
-        reject_unauthorized_connection
-      end
+      current_user || reject_unauthorized_connection
     end
   end
 end
diff --git a/app/channels/la_exercises_channel.rb b/app/channels/la_exercises_channel.rb
index 363da89b..a8821896 100644
--- a/app/channels/la_exercises_channel.rb
+++ b/app/channels/la_exercises_channel.rb
@@ -1,5 +1,6 @@
-class LaExercisesChannel < ApplicationCable::Channel
+# frozen_string_literal: true
 
+class LaExercisesChannel < ApplicationCable::Channel
   def subscribed
     stream_from specific_channel
   end
@@ -9,6 +10,7 @@ class LaExercisesChannel < ApplicationCable::Channel
   end
 
   private
+
   def specific_channel
     reject unless StudyGroupPolicy.new(current_user, StudyGroup.find_by(id: params[:study_group_id])).stream_la?
     "la_exercises_#{params[:exercise_id]}_channel_study_group_#{params[:study_group_id]}"
diff --git a/app/controllers/admin/dashboard_controller.rb b/app/controllers/admin/dashboard_controller.rb
index d5bc9d6b..f509bd53 100644
--- a/app/controllers/admin/dashboard_controller.rb
+++ b/app/controllers/admin/dashboard_controller.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Admin
   class DashboardController < ApplicationController
     include DashboardHelper
diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index a2927ef1..7bc90b9d 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -14,7 +14,8 @@ class ApplicationController < ActionController::Base
   rescue_from ActionController::InvalidAuthenticityToken, with: :render_csrf_error
 
   def current_user
-    ::NewRelic::Agent.add_custom_attributes(external_user_id: session[:external_user_id], session_user_id: session[:user_id])
+    ::NewRelic::Agent.add_custom_attributes(external_user_id: session[:external_user_id],
+session_user_id: session[:user_id])
     @current_user ||= ExternalUser.find_by(id: session[:external_user_id]) || login_from_session || login_from_other_sources || nil
   end
 
@@ -59,7 +60,7 @@ class ApplicationController < ActionController::Base
     respond_to do |format|
       format.html do
         # Prevent redirect loop
-        if request.url == request.referrer
+        if request.url == request.referer
           redirect_to :root, alert: message
         else
           redirect_back fallback_location: :root, allow_other_host: false, alert: message
diff --git a/app/controllers/code_ocean/files_controller.rb b/app/controllers/code_ocean/files_controller.rb
index dbced0b7..75bb8d0a 100644
--- a/app/controllers/code_ocean/files_controller.rb
+++ b/app/controllers/code_ocean/files_controller.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module CodeOcean
   class FilesController < ApplicationController
     include CommonBehavior
@@ -25,9 +27,10 @@ module CodeOcean
         if @object.save
           yield if block_given?
           path = options[:path].try(:call) || @object
-          respond_with_valid_object(format, notice: t('shared.object_created', model: @object.class.model_name.human), path: path, status: :created)
+          respond_with_valid_object(format, notice: t('shared.object_created', model: @object.class.model_name.human),
+path: path, status: :created)
         else
-          filename = (@object.path || '') + '/' + (@object.name || '') + (@object.file_type.try(:file_extension) || '')
+          filename = "#{@object.path || ''}/#{@object.name || ''}#{@object.file_type.try(:file_extension) || ''}"
           format.html { redirect_to(options[:path]); flash[:danger] = t('files.error.filename', name: filename) }
           format.json { render(json: @object.errors, status: :unprocessable_entity) }
         end
@@ -41,7 +44,10 @@ module CodeOcean
     end
 
     def file_params
-      params[:code_ocean_file].permit(file_attributes).merge(context_type: 'Submission', role: 'user_defined_file') if params[:code_ocean_file].present?
+      if params[:code_ocean_file].present?
+        params[:code_ocean_file].permit(file_attributes).merge(context_type: 'Submission',
+role: 'user_defined_file')
+      end
     end
     private :file_params
   end
diff --git a/app/controllers/codeharbor_links_controller.rb b/app/controllers/codeharbor_links_controller.rb
index 087f2736..019366e8 100644
--- a/app/controllers/codeharbor_links_controller.rb
+++ b/app/controllers/codeharbor_links_controller.rb
@@ -7,7 +7,8 @@ class CodeharborLinksController < ApplicationController
 
   def new
     base_url = CodeOcean::Config.new(:code_ocean).read[:codeharbor][:url] || ''
-    @codeharbor_link = CodeharborLink.new(push_url: base_url + '/import_exercise', check_uuid_url: base_url + '/import_uuid_check')
+    @codeharbor_link = CodeharborLink.new(push_url: "#{base_url}/import_exercise",
+check_uuid_url: "#{base_url}/import_uuid_check")
     authorize!
   end
 
diff --git a/app/controllers/comments_controller.rb b/app/controllers/comments_controller.rb
index fcddf876..32c31229 100644
--- a/app/controllers/comments_controller.rb
+++ b/app/controllers/comments_controller.rb
@@ -1,8 +1,10 @@
+# frozen_string_literal: true
+
 class CommentsController < ApplicationController
-  before_action :set_comment, only: [:show, :edit, :update, :destroy]
+  before_action :set_comment, only: %i[show edit update destroy]
 
   # to disable authorization check: comment the line below back in
- # skip_after_action :verify_authorized
+  # skip_after_action :verify_authorized
 
   def authorize!
     authorize(@comment || @comments)
@@ -12,16 +14,16 @@ class CommentsController < ApplicationController
   # GET /comments.json
   def index
     file = CodeOcean::File.find(params[:file_id])
-    #there might be no submission yet, so dont use find
+    # there might be no submission yet, so dont use find
     submission = Submission.find_by(id: file.context_id)
     if submission
       @comments = Comment.where(file_id: params[:file_id])
-      @comments.map{|comment|
+      @comments.map do |comment|
         comment.username = comment.user.displayname
         comment.date = comment.created_at.strftime('%d.%m.%Y %k:%M')
         comment.updated = (comment.created_at != comment.updated_at)
         comment.editable = comment.user == current_user
-      }
+      end
     else
       @comments = []
     end
@@ -81,9 +83,10 @@ class CommentsController < ApplicationController
 
   # Never trust parameters from the scary internet, only allow the white list through.
   def comment_params
-    #params.require(:comment).permit(:user_id, :file_id, :row, :column, :text)
+    # params.require(:comment).permit(:user_id, :file_id, :row, :column, :text)
     # fuer production mode, damit böse menschen keine falsche user_id uebergeben:
-    params.require(:comment).permit(:file_id, :row, :column, :text, :request_id).merge(user_id: current_user.id, user_type: current_user.class.name)
+    params.require(:comment).permit(:file_id, :row, :column, :text, :request_id).merge(user_id: current_user.id,
+user_type: current_user.class.name)
   end
 
   def send_mail_to_author(comment, request_for_comment)
@@ -96,15 +99,14 @@ class CommentsController < ApplicationController
     request_for_comment.commenters.each do |commenter|
       already_sent_mail = false
       subscriptions = Subscription.where(
-          :request_for_comment_id => request_for_comment.id,
-          :user_id => commenter.id, :user_type => commenter.class.name,
-          :deleted => false)
+          request_for_comment_id: request_for_comment.id,
+          user_id: commenter.id, user_type: commenter.class.name,
+          deleted: false
+        )
       subscriptions.each do |subscription|
-        if (subscription.subscription_type == 'author' and current_user == request_for_comment.user) or subscription.subscription_type == 'all'
-          unless subscription.user == current_user or already_sent_mail
-            UserMailer.got_new_comment_for_subscription(comment, subscription, current_user).deliver_now
-            already_sent_mail = true
-          end
+        if (((subscription.subscription_type == 'author') && (current_user == request_for_comment.user)) || (subscription.subscription_type == 'all')) && !((subscription.user == current_user) || already_sent_mail)
+          UserMailer.got_new_comment_for_subscription(comment, subscription, current_user).deliver_now
+          already_sent_mail = true
         end
       end
     end
diff --git a/app/controllers/concerns/common_behavior.rb b/app/controllers/concerns/common_behavior.rb
index a52c8b00..4c36cf63 100644
--- a/app/controllers/concerns/common_behavior.rb
+++ b/app/controllers/concerns/common_behavior.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module CommonBehavior
   def create_and_respond(options = {})
     @object = options[:object]
@@ -5,7 +7,8 @@ module CommonBehavior
       if @object.save
         yield if block_given?
         path = options[:path].try(:call) || @object
-        respond_with_valid_object(format, notice: t('shared.object_created', model: @object.class.model_name.human), path: path, status: :created)
+        respond_with_valid_object(format, notice: t('shared.object_created', model: @object.class.model_name.human),
+path: path, status: :created)
       else
         respond_with_invalid_object(format, template: :new)
       end
@@ -40,7 +43,8 @@ module CommonBehavior
     respond_to do |format|
       if @object.update(options[:params])
         path = options[:path] || @object
-        respond_with_valid_object(format, notice: t('shared.object_updated', model: @object.class.model_name.human), path: path, status: :ok)
+        respond_with_valid_object(format, notice: t('shared.object_updated', model: @object.class.model_name.human),
+path: path, status: :ok)
       else
         respond_with_invalid_object(format, template: :edit)
       end
diff --git a/app/controllers/concerns/file_parameters.rb b/app/controllers/concerns/file_parameters.rb
index 0236b1cb..0903ae74 100644
--- a/app/controllers/concerns/file_parameters.rb
+++ b/app/controllers/concerns/file_parameters.rb
@@ -15,7 +15,8 @@ module FileParameters
   private :reject_illegal_file_attributes
 
   def file_attributes
-    %w[content context_id feedback_message file_id file_type_id hidden id name native_file path read_only role weight file_template_id]
+    %w[content context_id feedback_message file_id file_type_id hidden id name native_file path read_only role weight
+       file_template_id]
   end
   private :file_attributes
 end
diff --git a/app/controllers/concerns/lti.rb b/app/controllers/concerns/lti.rb
index 6290d5a1..dbbc726f 100644
--- a/app/controllers/concerns/lti.rb
+++ b/app/controllers/concerns/lti.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'oauth/request_proxy/rack_request'
 
 module Lti
@@ -6,7 +8,7 @@ module Lti
 
   MAXIMUM_SCORE = 1
   MAXIMUM_SESSION_AGE = 60.minutes
-  SESSION_PARAMETERS = %w(launch_presentation_return_url lis_outcome_service_url lis_result_sourcedid)
+  SESSION_PARAMETERS = %w[launch_presentation_return_url lis_outcome_service_url lis_result_sourcedid].freeze
 
   def build_tool_provider(options = {})
     if options[:consumer] && options[:parameters]
@@ -20,7 +22,7 @@ module Lti
   # exercise_id.exists? ==> the user has submitted the results of an exercise to the consumer.
   # Only the lti_parameters are deleted.
   def clear_lti_session_data(exercise_id = nil, user_id = nil)
-    if (exercise_id.nil?)
+    if exercise_id.nil?
       session.delete(:external_user_id)
       session.delete(:study_group_id)
       session.delete(:embed_options)
@@ -48,27 +50,23 @@ module Lti
   def external_user_name(provider)
     # save person_name_full if supplied. this is the display_name, if it is set.
     # else only save the firstname, we don't want lastnames (family names)
-    if provider.lis_person_name_full
-      provider.lis_person_name_full
-    else
-      provider.lis_person_name_given
-    end
+    provider.lis_person_name_full || provider.lis_person_name_given
   end
 
   private :external_user_name
 
   def external_user_role(provider)
     result = 'learner'
-    unless provider.roles.blank?
+    if provider.roles.present?
       provider.roles.each do |role|
         case role.downcase
-        when 'administrator'
-          # We don't want anyone to get admin privileges through LTI
-          result = 'teacher' if result == 'learner'
-        when 'instructor'
-          result = 'teacher' if result == 'learner'
-        else # 'learner'
-          next
+          when 'administrator'
+            # We don't want anyone to get admin privileges through LTI
+            result = 'teacher' if result == 'learner'
+          when 'instructor'
+            result = 'teacher' if result == 'learner'
+          else # 'learner'
+            next
         end
       end
     end
@@ -141,7 +139,9 @@ module Lti
 
   def send_score(submission)
     ::NewRelic::Agent.add_custom_attributes({score: submission.normalized_score, session: session})
-    fail(Error, "Score #{submission.normalized_score} must be between 0 and #{MAXIMUM_SCORE}!") unless (0..MAXIMUM_SCORE).include?(submission.normalized_score)
+    unless (0..MAXIMUM_SCORE).cover?(submission.normalized_score)
+      raise Error.new("Score #{submission.normalized_score} must be between 0 and #{MAXIMUM_SCORE}!")
+    end
 
     if submission.user.consumer
       lti_parameter = LtiParameter.where(consumers_id: submission.user.consumer.id,
@@ -155,12 +155,12 @@ module Lti
       {status: 'error'}
     elsif provider.outcome_service?
       Sentry.set_extras({
-                            provider: provider.inspect,
+        provider: provider.inspect,
                             score: submission.normalized_score,
                             lti_parameter: lti_parameter.inspect,
                             session: session.to_hash,
-                            exercise_id: submission.exercise_id
-                          })
+                            exercise_id: submission.exercise_id,
+      })
       normalized_lit_score = submission.normalized_score
       if submission.before_deadline?
         # Keep the full score
@@ -170,11 +170,10 @@ module Lti
       elsif submission.after_late_deadline?
         # Reduce score by 100%
         normalized_lit_score *= 0.0
-      else # no deadline
-        # Keep the full score
       end
       response = provider.post_replace_result!(normalized_lit_score)
-      {code: response.response_code, message: response.post_response.body, status: response.code_major, score_sent: normalized_lit_score}
+      {code: response.response_code, message: response.post_response.body, status: response.code_major,
+score_sent: normalized_lit_score}
     else
       {status: 'unsupported'}
     end
@@ -186,22 +185,21 @@ module Lti
     @current_user = ExternalUser.find_or_create_by(consumer_id: @consumer.id, external_id: @provider.user_id)
     external_role = external_user_role(@provider)
     internal_role = @current_user.role
-    desired_role = internal_role != 'admin' ? external_role : internal_role
+    desired_role = internal_role == 'admin' ? internal_role : external_role
     # Update user with new information but change the role only if he is no admin user
     @current_user.update(email: external_user_email(@provider), name: external_user_name(@provider), role: desired_role)
   end
 
   private :set_current_user
 
-
   def set_study_group_membership
-    group = if not context_id?
-              StudyGroup.find_or_create_by(external_id: @provider.resource_link_id, consumer: @consumer)
-            else
+    group = if context_id?
               # Ensure to find the group independent of the name and set it only once.
               StudyGroup.find_or_create_by(external_id: @provider.context_id, consumer: @consumer) do |new_group|
                 new_group.name = @provider.context_title
               end
+            else
+              StudyGroup.find_or_create_by(external_id: @provider.resource_link_id, consumer: @consumer)
             end
     group.external_users << @current_user unless group.external_users.include? @current_user
     group.save
diff --git a/app/controllers/concerns/remote_evaluation_parameters.rb b/app/controllers/concerns/remote_evaluation_parameters.rb
index a88ef7ea..0f0c9222 100644
--- a/app/controllers/concerns/remote_evaluation_parameters.rb
+++ b/app/controllers/concerns/remote_evaluation_parameters.rb
@@ -1,8 +1,13 @@
+# frozen_string_literal: true
+
 module RemoteEvaluationParameters
   include FileParameters
 
   def remote_evaluation_params
-    remote_evaluation_params = params[:remote_evaluation].permit(:validation_token, files_attributes: file_attributes) if params[:remote_evaluation].present?
+    if params[:remote_evaluation].present?
+      remote_evaluation_params = params[:remote_evaluation].permit(:validation_token,
+        files_attributes: file_attributes)
+    end
   end
   private :remote_evaluation_params
-end
\ No newline at end of file
+end
diff --git a/app/controllers/concerns/submission_parameters.rb b/app/controllers/concerns/submission_parameters.rb
index 1def6759..12a37ec0 100644
--- a/app/controllers/concerns/submission_parameters.rb
+++ b/app/controllers/concerns/submission_parameters.rb
@@ -4,7 +4,12 @@ module SubmissionParameters
   include FileParameters
 
   def submission_params
-    submission_params = params[:submission].present? ? params[:submission].permit(:cause, :exercise_id, files_attributes: file_attributes) : {}
+    submission_params = if params[:submission].present?
+                          params[:submission].permit(:cause, :exercise_id,
+                            files_attributes: file_attributes)
+                        else
+                          {}
+                        end
     submission_params = merge_user(submission_params)
     files_attributes = submission_params[:files_attributes]
     exercise = Exercise.find_by(id: submission_params[:exercise_id])
diff --git a/app/controllers/concerns/submission_scoring.rb b/app/controllers/concerns/submission_scoring.rb
index b04f0fe2..2fa4fae9 100644
--- a/app/controllers/concerns/submission_scoring.rb
+++ b/app/controllers/concerns/submission_scoring.rb
@@ -12,8 +12,8 @@ module SubmissionScoring
         output = execute_test_file(file, submission)
         assessment = assessor.assess(output)
         passed = ((assessment[:passed] == assessment[:count]) and (assessment[:score]).positive?)
-        testrun_output = passed ? nil : 'status: ' + output[:status].to_s + "\n stdout: " + output[:stdout].to_s + "\n stderr: " + output[:stderr].to_s
-        unless testrun_output.blank?
+        testrun_output = passed ? nil : "status: #{output[:status]}\n stdout: #{output[:stdout]}\n stderr: #{output[:stderr]}"
+        if testrun_output.present?
           submission.exercise.execution_environment.error_templates.each do |template|
             pattern = Regexp.new(template.signature).freeze
             StructuredError.create_from_template(template, testrun_output, submission) if pattern.match(testrun_output)
@@ -50,7 +50,8 @@ module SubmissionScoring
   private :collect_test_results
 
   def execute_test_file(file, submission)
-    DockerClient.new(execution_environment: file.context.execution_environment).execute_test_command(submission, file.name_with_extension)
+    DockerClient.new(execution_environment: file.context.execution_environment).execute_test_command(submission,
+      file.name_with_extension)
   end
 
   private :execute_test_file
@@ -69,17 +70,21 @@ module SubmissionScoring
   def score_submission(submission)
     outputs = collect_test_results(submission)
     score = 0.0
-    unless outputs.nil? || outputs.empty?
+    if outputs.present?
       outputs.each do |output|
         score += output[:score] * output[:weight] unless output.nil?
 
-        output[:stderr] += "\n\n#{t('exercises.editor.timeout', permitted_execution_time: submission.exercise.execution_environment.permitted_execution_time.to_s)}" if output.present? && output[:status] == :timeout
+        if output.present? && output[:status] == :timeout
+          output[:stderr] += "\n\n#{t('exercises.editor.timeout',
+            permitted_execution_time: submission.exercise.execution_environment.permitted_execution_time.to_s)}"
+        end
       end
     end
     submission.update(score: score)
     if submission.normalized_score == 1.0
       Thread.new do
-        RequestForComment.where(exercise_id: submission.exercise_id, user_id: submission.user_id, user_type: submission.user_type).each do |rfc|
+        RequestForComment.where(exercise_id: submission.exercise_id, user_id: submission.user_id,
+user_type: submission.user_type).each do |rfc|
           rfc.full_score_reached = true
           rfc.save
         end
diff --git a/app/controllers/consumers_controller.rb b/app/controllers/consumers_controller.rb
index 2a2f784a..a58424a0 100644
--- a/app/controllers/consumers_controller.rb
+++ b/app/controllers/consumers_controller.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ConsumersController < ApplicationController
   include CommonBehavior
 
@@ -18,8 +20,7 @@ class ConsumersController < ApplicationController
     destroy_and_respond(object: @consumer)
   end
 
-  def edit
-  end
+  def edit; end
 
   def consumer_params
     params[:consumer].permit(:name, :oauth_key, :oauth_secret) if params[:consumer].present?
@@ -42,8 +43,7 @@ class ConsumersController < ApplicationController
   end
   private :set_consumer
 
-  def show
-  end
+  def show; end
 
   def update
     update_and_respond(object: @consumer, params: consumer_params)
diff --git a/app/controllers/error_template_attributes_controller.rb b/app/controllers/error_template_attributes_controller.rb
index 283e5b03..425c69d4 100644
--- a/app/controllers/error_template_attributes_controller.rb
+++ b/app/controllers/error_template_attributes_controller.rb
@@ -1,5 +1,7 @@
+# frozen_string_literal: true
+
 class ErrorTemplateAttributesController < ApplicationController
-  before_action :set_error_template_attribute, only: [:show, :edit, :update, :destroy]
+  before_action :set_error_template_attribute, only: %i[show edit update destroy]
 
   def authorize!
     authorize(@error_template_attributes || @error_template_attribute)
@@ -9,7 +11,8 @@ class ErrorTemplateAttributesController < ApplicationController
   # GET /error_template_attributes
   # GET /error_template_attributes.json
   def index
-    @error_template_attributes = ErrorTemplateAttribute.all.order('important DESC', :key, :id).paginate(page: params[:page])
+    @error_template_attributes = ErrorTemplateAttribute.all.order('important DESC', :key,
+      :id).paginate(page: params[:page])
     authorize!
   end
 
@@ -38,7 +41,9 @@ class ErrorTemplateAttributesController < ApplicationController
 
     respond_to do |format|
       if @error_template_attribute.save
-        format.html { redirect_to @error_template_attribute, notice: 'Error template attribute was successfully created.' }
+        format.html do
+          redirect_to @error_template_attribute, notice: 'Error template attribute was successfully created.'
+        end
         format.json { render :show, status: :created, location: @error_template_attribute }
       else
         format.html { render :new }
@@ -53,7 +58,9 @@ class ErrorTemplateAttributesController < ApplicationController
     authorize!
     respond_to do |format|
       if @error_template_attribute.update(error_template_attribute_params)
-        format.html { redirect_to @error_template_attribute, notice: 'Error template attribute was successfully updated.' }
+        format.html do
+          redirect_to @error_template_attribute, notice: 'Error template attribute was successfully updated.'
+        end
         format.json { render :show, status: :ok, location: @error_template_attribute }
       else
         format.html { render :edit }
@@ -68,19 +75,25 @@ class ErrorTemplateAttributesController < ApplicationController
     authorize!
     @error_template_attribute.destroy
     respond_to do |format|
-      format.html { redirect_to error_template_attributes_url, notice: 'Error template attribute was successfully destroyed.' }
+      format.html do
+        redirect_to error_template_attributes_url, notice: 'Error template attribute was successfully destroyed.'
+      end
       format.json { head :no_content }
     end
   end
 
   private
-    # Use callbacks to share common setup or constraints between actions.
-    def set_error_template_attribute
-      @error_template_attribute = ErrorTemplateAttribute.find(params[:id])
-    end
 
-    # Never trust parameters from the scary internet, only allow the white list through.
-    def error_template_attribute_params
-      params[:error_template_attribute].permit(:key, :description, :regex, :important) if params[:error_template_attribute].present?
+  # Use callbacks to share common setup or constraints between actions.
+  def set_error_template_attribute
+    @error_template_attribute = ErrorTemplateAttribute.find(params[:id])
+  end
+
+  # Never trust parameters from the scary internet, only allow the white list through.
+  def error_template_attribute_params
+    if params[:error_template_attribute].present?
+      params[:error_template_attribute].permit(:key, :description, :regex,
+        :important)
     end
+  end
 end
diff --git a/app/controllers/error_templates_controller.rb b/app/controllers/error_templates_controller.rb
index bec956d8..654f97a7 100644
--- a/app/controllers/error_templates_controller.rb
+++ b/app/controllers/error_templates_controller.rb
@@ -1,5 +1,7 @@
+# frozen_string_literal: true
+
 class ErrorTemplatesController < ApplicationController
-  before_action :set_error_template, only: [:show, :edit, :update, :destroy, :add_attribute, :remove_attribute]
+  before_action :set_error_template, only: %i[show edit update destroy add_attribute remove_attribute]
 
   def authorize!
     authorize(@error_templates || @error_template)
@@ -92,13 +94,17 @@ class ErrorTemplatesController < ApplicationController
   end
 
   private
-    # Use callbacks to share common setup or constraints between actions.
-    def set_error_template
-      @error_template = ErrorTemplate.find(params[:id])
-    end
 
-    # Never trust parameters from the scary internet, only allow the white list through.
-    def error_template_params
-      params[:error_template].permit(:name, :execution_environment_id, :signature, :description, :hint) if params[:error_template].present?
+  # Use callbacks to share common setup or constraints between actions.
+  def set_error_template
+    @error_template = ErrorTemplate.find(params[:id])
+  end
+
+  # Never trust parameters from the scary internet, only allow the white list through.
+  def error_template_params
+    if params[:error_template].present?
+      params[:error_template].permit(:name, :execution_environment_id, :signature, :description,
+        :hint)
     end
+  end
 end
diff --git a/app/controllers/execution_environments_controller.rb b/app/controllers/execution_environments_controller.rb
index b373926a..eff99068 100644
--- a/app/controllers/execution_environments_controller.rb
+++ b/app/controllers/execution_environments_controller.rb
@@ -1,9 +1,11 @@
+# frozen_string_literal: true
+
 class ExecutionEnvironmentsController < ApplicationController
   include CommonBehavior
 
-  before_action :set_docker_images, only: [:create, :edit, :new, :update]
-  before_action :set_execution_environment, only: MEMBER_ACTIONS + [:execute_command, :shell, :statistics]
-  before_action :set_testing_framework_adapters, only: [:create, :edit, :new, :update]
+  before_action :set_docker_images, only: %i[create edit new update]
+  before_action :set_execution_environment, only: MEMBER_ACTIONS + %i[execute_command shell statistics]
+  before_action :set_testing_framework_adapters, only: %i[create edit new update]
 
   def authorize!
     authorize(@execution_environment || @execution_environments)
@@ -20,17 +22,15 @@ class ExecutionEnvironmentsController < ApplicationController
     destroy_and_respond(object: @execution_environment)
   end
 
-  def edit
-  end
+  def edit; end
 
   def execute_command
     @docker_client = DockerClient.new(execution_environment: @execution_environment)
     render(json: @docker_client.execute_arbitrary_command(params[:command]))
   end
 
-
   def working_time_query
-    """
+    "
       SELECT exercise_id, avg(working_time) as average_time, stddev_samp(extract('epoch' from working_time)) * interval '1 second' as stddev_time
       FROM
         (
@@ -52,11 +52,11 @@ class ExecutionEnvironmentsController < ApplicationController
             GROUP BY exercise_id, user_id, id) AS foo) AS bar
       GROUP BY user_id, exercise_id
     ) AS baz GROUP BY exercise_id;
-    """
+    "
   end
 
   def user_query
-    """
+    "
     SELECT
       id AS exercise_id,
       COUNT(DISTINCT user_id) AS users,
@@ -79,7 +79,7 @@ class ExecutionEnvironmentsController < ApplicationController
        GROUP BY e.id,
                 s.user_id) AS inner_query
     GROUP BY id;
-    """
+    "
   end
 
   def statistics
@@ -87,21 +87,25 @@ class ExecutionEnvironmentsController < ApplicationController
     user_statistics = {}
 
     ApplicationRecord.connection.execute(working_time_query).each do |tuple|
-      working_time_statistics[tuple["exercise_id"].to_i] = tuple
+      working_time_statistics[tuple['exercise_id'].to_i] = tuple
     end
 
     ApplicationRecord.connection.execute(user_query).each do |tuple|
-      user_statistics[tuple["exercise_id"].to_i] = tuple
+      user_statistics[tuple['exercise_id'].to_i] = tuple
     end
 
     render locals: {
       working_time_statistics: working_time_statistics,
-      user_statistics: user_statistics
+      user_statistics: user_statistics,
     }
   end
 
   def execution_environment_params
-    params[:execution_environment].permit(:docker_image, :exposed_ports, :editor_mode, :file_extension, :file_type_id, :help, :indent_size, :memory_limit, :name, :network_enabled, :permitted_execution_time, :pool_size, :run_command, :test_command, :testing_framework).merge(user_id: current_user.id, user_type: current_user.class.name) if params[:execution_environment].present?
+    if params[:execution_environment].present?
+      params[:execution_environment].permit(:docker_image, :exposed_ports, :editor_mode, :file_extension, :file_type_id, :help, :indent_size, :memory_limit, :name, :network_enabled, :permitted_execution_time, :pool_size, :run_command, :test_command, :testing_framework).merge(
+user_id: current_user.id, user_type: current_user.class.name
+)
+    end
   end
   private :execution_environment_params
 
@@ -118,10 +122,10 @@ class ExecutionEnvironmentsController < ApplicationController
   def set_docker_images
     DockerClient.check_availability!
     @docker_images = DockerClient.image_tags.sort
-  rescue DockerClient::Error => error
+  rescue DockerClient::Error => e
     @docker_images = []
-    flash[:warning] = error.message
-    Sentry.capture_exception(error)
+    flash[:warning] = e.message
+    Sentry.capture_exception(e)
   end
   private :set_docker_images
 
@@ -139,8 +143,7 @@ class ExecutionEnvironmentsController < ApplicationController
   end
   private :set_testing_framework_adapters
 
-  def shell
-  end
+  def shell; end
 
   def show
     if @execution_environment.testing_framework?
diff --git a/app/controllers/exercise_collections_controller.rb b/app/controllers/exercise_collections_controller.rb
index 3e13a3af..b61d0334 100644
--- a/app/controllers/exercise_collections_controller.rb
+++ b/app/controllers/exercise_collections_controller.rb
@@ -1,15 +1,16 @@
+# frozen_string_literal: true
+
 class ExerciseCollectionsController < ApplicationController
   include CommonBehavior
 
-  before_action :set_exercise_collection, only: [:show, :edit, :update, :destroy, :statistics]
+  before_action :set_exercise_collection, only: %i[show edit update destroy statistics]
 
   def index
-    @exercise_collections = ExerciseCollection.all.paginate(:page => params[:page])
+    @exercise_collections = ExerciseCollection.all.paginate(page: params[:page])
     authorize!
   end
 
-  def show
-  end
+  def show; end
 
   def new
     @exercise_collection = ExerciseCollection.new
@@ -28,16 +29,14 @@ class ExerciseCollectionsController < ApplicationController
     destroy_and_respond(object: @exercise_collection)
   end
 
-  def edit
-  end
+  def edit; end
 
   def update
     authorize!
     update_and_respond(object: @exercise_collection, params: exercise_collection_params)
   end
 
-  def statistics
-  end
+  def statistics; end
 
   private
 
@@ -51,8 +50,18 @@ class ExerciseCollectionsController < ApplicationController
   end
 
   def exercise_collection_params
-    sanitized_params = params[:exercise_collection].present? ? params[:exercise_collection].permit(:name, :use_anomaly_detection, :user_id, :user_type, :exercise_ids => []).merge(user_type: InternalUser.name) : {}
-    sanitized_params[:exercise_ids] = sanitized_params[:exercise_ids].reject {|v| v.nil? or v == ''}
-    sanitized_params.tap {|p| p[:exercise_collection_items] = p[:exercise_ids].map.with_index {|_id, index| ExerciseCollectionItem.find_or_create_by(exercise_id: _id, exercise_collection_id: @exercise_collection.id, position: index)}; p.delete(:exercise_ids)}
+    sanitized_params = if params[:exercise_collection].present?
+                         params[:exercise_collection].permit(:name,
+                           :use_anomaly_detection, :user_id, :user_type, exercise_ids: []).merge(user_type: InternalUser.name)
+                       else
+                         {}
+                       end
+    sanitized_params[:exercise_ids] = sanitized_params[:exercise_ids].reject {|v| v.nil? or v == '' }
+    sanitized_params.tap do |p|
+      p[:exercise_collection_items] = p[:exercise_ids].map.with_index do |_id, index|
+        ExerciseCollectionItem.find_or_create_by(exercise_id: _id, exercise_collection_id: @exercise_collection.id, position: index)
+      end
+      p.delete(:exercise_ids)
+    end
   end
 end
diff --git a/app/controllers/exercises_controller.rb b/app/controllers/exercises_controller.rb
index b26ee75b..07a75fd9 100644
--- a/app/controllers/exercises_controller.rb
+++ b/app/controllers/exercises_controller.rb
@@ -9,15 +9,19 @@ class ExercisesController < ApplicationController
 
   before_action :handle_file_uploads, only: %i[create update]
   before_action :set_execution_environments, only: %i[create edit new update]
-  before_action :set_exercise_and_authorize, only: MEMBER_ACTIONS + %i[clone implement working_times intervention search run statistics submit reload feedback requests_for_comments study_group_dashboard export_external_check export_external_confirm]
+  before_action :set_exercise_and_authorize,
+    only: MEMBER_ACTIONS + %i[clone implement working_times intervention search run statistics submit reload feedback
+                              requests_for_comments study_group_dashboard export_external_check export_external_confirm]
   before_action :set_external_user_and_authorize, only: [:statistics]
   before_action :set_file_types, only: %i[create edit new update]
   before_action :set_course_token, only: [:implement]
   before_action :set_available_tips, only: %i[implement show new edit]
 
-  skip_before_action :verify_authenticity_token, only: %i[import_exercise import_uuid_check export_external_confirm export_external_check]
+  skip_before_action :verify_authenticity_token,
+    only: %i[import_exercise import_uuid_check export_external_confirm export_external_check]
   skip_after_action :verify_authorized, only: %i[import_exercise import_uuid_check export_external_confirm]
-  skip_after_action :verify_policy_scoped, only: %i[import_exercise import_uuid_check export_external_confirm], raise: false
+  skip_after_action :verify_policy_scoped, only: %i[import_exercise import_uuid_check export_external_confirm],
+raise: false
 
   def authorize!
     authorize(@exercise || @exercises)
@@ -72,8 +76,8 @@ class ExercisesController < ApplicationController
     return if performed?
 
     myparam = exercise_params.presence || {}
-    checked_exercise_tags = @exercise_tags.select { |et| myparam[:tag_ids].include? et.tag.id.to_s }
-    removed_exercise_tags = @exercise_tags.reject { |et| myparam[:tag_ids].include? et.tag.id.to_s }
+    checked_exercise_tags = @exercise_tags.select {|et| myparam[:tag_ids].include? et.tag.id.to_s }
+    removed_exercise_tags = @exercise_tags.reject {|et| myparam[:tag_ids].include? et.tag.id.to_s }
 
     checked_exercise_tags.each do |et|
       et.factor = params[:tag_factors][et.tag_id.to_s][:factor]
@@ -106,7 +110,8 @@ class ExercisesController < ApplicationController
   end
 
   def export_external_check
-    codeharbor_check = ExerciseService::CheckExternal.call(uuid: @exercise.uuid, codeharbor_link: current_user.codeharbor_link)
+    codeharbor_check = ExerciseService::CheckExternal.call(uuid: @exercise.uuid,
+codeharbor_link: current_user.codeharbor_link)
     render json: {
       message: codeharbor_check[:message],
       actions: render_to_string(
@@ -116,9 +121,9 @@ class ExercisesController < ApplicationController
           exercise_found: codeharbor_check[:exercise_found],
           update_right: codeharbor_check[:update_right],
           error: codeharbor_check[:error],
-          exported: false
+          exported: false,
         }
-      )
+      ),
     }, status: :ok
   end
 
@@ -133,14 +138,16 @@ class ExercisesController < ApplicationController
       render json: {
         status: 'success',
         message: t('exercises.export_codeharbor.successfully_exported', id: @exercise.id, title: @exercise.title),
-        actions: render_to_string(partial: 'export_actions', locals: {exercise: @exercise, exported: true, error: error})
+        actions: render_to_string(partial: 'export_actions',
+locals: {exercise: @exercise, exported: true, error: error}),
       }
       @exercise.save
     else
       render json: {
         status: 'fail',
         message: t('exercises.export_codeharbor.export_failed', id: @exercise.id, title: @exercise.title, error: error),
-        actions: render_to_string(partial: 'export_actions', locals: {exercise: @exercise, exported: true, error: error})
+        actions: render_to_string(partial: 'export_actions',
+locals: {exercise: @exercise, exported: true, error: error}),
       }
     end
   end
@@ -177,7 +184,7 @@ class ExercisesController < ApplicationController
     render json: t('exercises.import_codeharbor.import_errors.invalid'), status: :bad_request
   rescue StandardError => e
     Sentry.capture_exception(e)
-    render json: t('exercises.import_codeharbor.import_errors.internal_error'), status: 500
+    render json: t('exercises.import_codeharbor.import_errors.internal_error'), status: :internal_server_error
   end
 
   def user_from_api_key
@@ -194,7 +201,11 @@ class ExercisesController < ApplicationController
   private :user_by_codeharbor_token
 
   def exercise_params
-    params[:exercise].permit(:description, :execution_environment_id, :file_id, :instructions, :submission_deadline, :late_submission_deadline, :public, :unpublished, :hide_file_tree, :allow_file_creation, :allow_auto_completion, :title, :expected_difficulty, :tips, files_attributes: file_attributes, tag_ids: []).merge(user_id: current_user.id, user_type: current_user.class.name) if params[:exercise].present?
+    if params[:exercise].present?
+      params[:exercise].permit(:description, :execution_environment_id, :file_id, :instructions, :submission_deadline, :late_submission_deadline, :public, :unpublished, :hide_file_tree, :allow_file_creation, :allow_auto_completion, :title, :expected_difficulty, :tips, files_attributes: file_attributes, tag_ids: []).merge(
+user_id: current_user.id, user_type: current_user.class.name
+)
+    end
   end
   private :exercise_params
 
@@ -261,8 +272,10 @@ class ExercisesController < ApplicationController
     redirect_to(@exercise, alert: t('exercises.implement.unpublished')) if @exercise.unpublished? && current_user.role != 'admin' && current_user.role != 'teacher' # TODO: TESTESTEST
     redirect_to(@exercise, alert: t('exercises.implement.no_files')) unless @exercise.files.visible.exists?
     user_solved_exercise = @exercise.has_user_solved(current_user)
-    count_interventions_today = UserExerciseIntervention.where(user: current_user).where('created_at >= ?', Time.zone.now.beginning_of_day).count
-    user_got_intervention_in_exercise = UserExerciseIntervention.where(user: current_user, exercise: @exercise).size >= max_intervention_count_per_exercise
+    count_interventions_today = UserExerciseIntervention.where(user: current_user).where('created_at >= ?',
+      Time.zone.now.beginning_of_day).count
+    user_got_intervention_in_exercise = UserExerciseIntervention.where(user: current_user,
+exercise: @exercise).size >= max_intervention_count_per_exercise
     (user_got_enough_interventions = count_interventions_today >= max_intervention_count_per_day) || user_got_intervention_in_exercise
 
     if @embed_options[:disable_interventions]
@@ -331,14 +344,15 @@ class ExercisesController < ApplicationController
     end
 
     # Return an array with top-level tips
-    @tips = nested_tips.values.select { |tip| tip.parent_exercise_tip_id.nil? }
+    @tips = nested_tips.values.select {|tip| tip.parent_exercise_tip_id.nil? }
   end
   private :set_available_tips
 
   def working_times
     working_time_accumulated = @exercise.accumulated_working_time_for_only(current_user)
     working_time_75_percentile = @exercise.get_quantiles([0.75]).first
-    render(json: {working_time_75_percentile: working_time_75_percentile, working_time_accumulated: working_time_accumulated})
+    render(json: {working_time_75_percentile: working_time_75_percentile,
+working_time_accumulated: working_time_accumulated})
   end
 
   def intervention
@@ -436,7 +450,9 @@ class ExercisesController < ApplicationController
     checked_exercise_tags = @exercise.exercise_tags
     checked_tags = checked_exercise_tags.collect(&:tag).to_set
     unchecked_tags = Tag.all.to_set.subtract checked_tags
-    @exercise_tags = checked_exercise_tags + unchecked_tags.collect { |tag| ExerciseTag.new(exercise: @exercise, tag: tag) }
+    @exercise_tags = checked_exercise_tags + unchecked_tags.collect do |tag|
+                                               ExerciseTag.new(exercise: @exercise, tag: tag)
+                                             end
   end
   private :collect_set_and_unset_exercise_tags
 
@@ -453,8 +469,10 @@ class ExercisesController < ApplicationController
       # Render statistics page for one specific external user
       authorize(@external_user, :statistics?)
       if policy(@exercise).detailed_statistics?
-        @submissions = Submission.where(user: @external_user, exercise_id: @exercise.id).in_study_group_of(current_user).order('created_at')
-        interventions = UserExerciseIntervention.where('user_id = ?  AND exercise_id = ?', @external_user.id, @exercise.id)
+        @submissions = Submission.where(user: @external_user,
+exercise_id: @exercise.id).in_study_group_of(current_user).order('created_at')
+        interventions = UserExerciseIntervention.where('user_id = ?  AND exercise_id = ?', @external_user.id,
+          @exercise.id)
         @all_events = (@submissions + interventions).sort_by(&:created_at)
         @deltas = @all_events.map.with_index do |item, index|
           delta = item.created_at - @all_events[index - 1].created_at if index.positive?
@@ -465,7 +483,8 @@ class ExercisesController < ApplicationController
           @working_times_until.push((format_time_difference(@deltas[0..index].inject(:+)) if index.positive?))
         end
       else
-        final_submissions = Submission.where(user: @external_user, exercise_id: @exercise.id).in_study_group_of(current_user).final
+        final_submissions = Submission.where(user: @external_user,
+exercise_id: @exercise.id).in_study_group_of(current_user).final
         @submissions = []
         %i[before_deadline within_grace_period after_late_deadline].each do |filter|
           relevant_submission = final_submissions.send(filter).latest
@@ -492,7 +511,7 @@ class ExercisesController < ApplicationController
         user_statistics[tuple['user_id'].to_i] = tuple
       end
       render locals: {
-        user_statistics: user_statistics
+        user_statistics: user_statistics,
       }
     end
   end
@@ -508,7 +527,8 @@ class ExercisesController < ApplicationController
   end
 
   def transmit_lti_score
-    ::NewRelic::Agent.add_custom_attributes({submission: @submission.id, normalized_score: @submission.normalized_score})
+    ::NewRelic::Agent.add_custom_attributes({submission: @submission.id,
+normalized_score: @submission.normalized_score})
     response = send_score(@submission)
 
     if response[:status] == 'success'
@@ -533,8 +553,8 @@ class ExercisesController < ApplicationController
     return if performed?
 
     myparam = exercise_params
-    checked_exercise_tags = @exercise_tags.select { |et| myparam[:tag_ids].include? et.tag.id.to_s }
-    removed_exercise_tags = @exercise_tags.reject { |et| myparam[:tag_ids].include? et.tag.id.to_s }
+    checked_exercise_tags = @exercise_tags.select {|et| myparam[:tag_ids].include? et.tag.id.to_s }
+    removed_exercise_tags = @exercise_tags.reject {|et| myparam[:tag_ids].include? et.tag.id.to_s }
 
     checked_exercise_tags.each do |et|
       et.factor = params[:tag_factors][et.tag_id.to_s][:factor]
@@ -624,9 +644,9 @@ class ExercisesController < ApplicationController
     authorize!
     @study_group_id = params[:study_group_id]
     @request_for_comments = RequestForComment
-                            .where(exercise: @exercise).includes(:submission)
-                            .where(submissions: {study_group_id: @study_group_id})
-                            .order(created_at: :desc)
+      .where(exercise: @exercise).includes(:submission)
+      .where(submissions: {study_group_id: @study_group_id})
+      .order(created_at: :desc)
 
     @graph_data = @exercise.get_working_times_for_study_group(@study_group_id)
   end
diff --git a/app/controllers/external_users_controller.rb b/app/controllers/external_users_controller.rb
index 7b3e1a91..b5609c9e 100644
--- a/app/controllers/external_users_controller.rb
+++ b/app/controllers/external_users_controller.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ExternalUsersController < ApplicationController
   before_action :require_user!
 
@@ -17,8 +19,8 @@ class ExternalUsersController < ApplicationController
     authorize!
   end
 
-  def working_time_query(tag=nil)
-    """
+  def working_time_query(tag = nil)
+    "
     SELECT user_id,
            bar.exercise_id,
            max(score) as maximum_score,
@@ -43,16 +45,16 @@ class ExternalUsersController < ApplicationController
           FROM submissions
           WHERE user_id = #{@user.id}
             AND user_type = 'ExternalUser'
-          #{!current_user.admin? ? "AND study_group_id IN (#{current_user.study_groups.pluck(:id).join(', ')}) AND cause = 'submit'" : ''}
+          #{current_user.admin? ? '' : "AND study_group_id IN (#{current_user.study_groups.pluck(:id).join(', ')}) AND cause = 'submit'"}
           GROUP BY exercise_id,
                    user_id,
                    id
           ) AS foo
       ) AS bar
-    #{tag.nil? ? '' : ' JOIN exercise_tags et ON et.exercise_id = bar.exercise_id AND et.tag_id = ' + tag + ' '}
+    #{tag.nil? ? '' : " JOIN exercise_tags et ON et.exercise_id = bar.exercise_id AND et.tag_id = #{tag} "}
     GROUP BY user_id,
              bar.exercise_id;
-    """
+    "
   end
 
   def statistics
@@ -62,11 +64,11 @@ class ExternalUsersController < ApplicationController
     statistics = {}
 
     ApplicationRecord.connection.execute(working_time_query(params[:tag])).each do |tuple|
-      statistics[tuple["exercise_id"].to_i] = tuple
+      statistics[tuple['exercise_id'].to_i] = tuple
     end
 
     render locals: {
-      statistics: statistics
+      statistics: statistics,
     }
   end
 
@@ -75,15 +77,15 @@ class ExternalUsersController < ApplicationController
     authorize!
 
     statistics = []
-    tags = ProxyExercise.new().get_user_knowledge_and_max_knowledge(@user, @user.participations.uniq.compact)
+    tags = ProxyExercise.new.get_user_knowledge_and_max_knowledge(@user, @user.participations.uniq.compact)
     tags[:user_topic_knowledge].each_pair do |tag, value|
-      statistics.append({key: tag.name.to_s, value: (100.0 / tags[:max_topic_knowledge][tag] * value).round, id: tag.id})
+      statistics.append({key: tag.name.to_s, value: (100.0 / tags[:max_topic_knowledge][tag] * value).round,
+id: tag.id})
     end
-    statistics.sort_by! {|item| -item[:value]}
+    statistics.sort_by! {|item| -item[:value] }
 
     respond_to do |format|
       format.json { render(json: statistics) }
     end
   end
-
 end
diff --git a/app/controllers/file_templates_controller.rb b/app/controllers/file_templates_controller.rb
index 04c2a98a..da1ae5b1 100644
--- a/app/controllers/file_templates_controller.rb
+++ b/app/controllers/file_templates_controller.rb
@@ -1,5 +1,7 @@
+# frozen_string_literal: true
+
 class FileTemplatesController < ApplicationController
-  before_action :set_file_template, only: [:show, :edit, :update, :destroy]
+  before_action :set_file_template, only: %i[show edit update destroy]
 
   def authorize!
     authorize(@file_template || @file_templates)
@@ -7,7 +9,7 @@ class FileTemplatesController < ApplicationController
   private :authorize!
 
   def by_file_type
-    @file_templates = FileTemplate.where(:file_type_id => params[:file_type_id])
+    @file_templates = FileTemplate.where(file_type_id: params[:file_type_id])
     authorize!
     respond_to do |format|
       format.json { render :show, status: :ok, json: @file_templates.to_json }
@@ -82,13 +84,14 @@ class FileTemplatesController < ApplicationController
   end
 
   private
-    # Use callbacks to share common setup or constraints between actions.
-    def set_file_template
-      @file_template = FileTemplate.find(params[:id])
-    end
 
-    # Never trust parameters from the scary internet, only allow the white list through.
-    def file_template_params
-      params[:file_template].permit(:name, :file_type_id, :content) if params[:file_template].present?
-    end
+  # Use callbacks to share common setup or constraints between actions.
+  def set_file_template
+    @file_template = FileTemplate.find(params[:id])
+  end
+
+  # Never trust parameters from the scary internet, only allow the white list through.
+  def file_template_params
+    params[:file_template].permit(:name, :file_type_id, :content) if params[:file_template].present?
+  end
 end
diff --git a/app/controllers/file_types_controller.rb b/app/controllers/file_types_controller.rb
index d450df3d..53228ce6 100644
--- a/app/controllers/file_types_controller.rb
+++ b/app/controllers/file_types_controller.rb
@@ -1,7 +1,9 @@
+# frozen_string_literal: true
+
 class FileTypesController < ApplicationController
   include CommonBehavior
 
-  before_action :set_editor_modes, only: [:create, :edit, :new, :update]
+  before_action :set_editor_modes, only: %i[create edit new update]
   before_action :set_file_type, only: MEMBER_ACTIONS
 
   def authorize!
@@ -19,11 +21,14 @@ class FileTypesController < ApplicationController
     destroy_and_respond(object: @file_type)
   end
 
-  def edit
-  end
+  def edit; end
 
   def file_type_params
-    params[:file_type].permit(:binary, :editor_mode, :executable, :file_extension, :name, :indent_size, :renderable).merge(user_id: current_user.id, user_type: current_user.class.name) if params[:file_type].present?
+    if params[:file_type].present?
+      params[:file_type].permit(:binary, :editor_mode, :executable, :file_extension, :name, :indent_size, :renderable).merge(
+user_id: current_user.id, user_type: current_user.class.name
+)
+    end
   end
   private :file_type_params
 
@@ -39,7 +44,7 @@ class FileTypesController < ApplicationController
 
   def set_editor_modes
     @editor_modes = Dir.glob('vendor/assets/javascripts/ace/mode-*.js').sort.map do |filename|
-      name = filename.gsub(/\w+\/|mode-|.js$/, '')
+      name = filename.gsub(%r{\w+/|mode-|.js$}, '')
       [name, "ace/mode/#{name}"]
     end
   end
@@ -51,8 +56,7 @@ class FileTypesController < ApplicationController
   end
   private :set_file_type
 
-  def show
-  end
+  def show; end
 
   def update
     update_and_respond(object: @file_type, params: file_type_params)
diff --git a/app/controllers/flowr_controller.rb b/app/controllers/flowr_controller.rb
index 310d91d2..b507d174 100644
--- a/app/controllers/flowr_controller.rb
+++ b/app/controllers/flowr_controller.rb
@@ -1,11 +1,12 @@
-class FlowrController < ApplicationController
+# frozen_string_literal: true
 
+class FlowrController < ApplicationController
   def insights
     require_user!
     # get the latest submission for this user that also has a test run (i.e. structured_errors if applicable)
     submission = Submission.joins(:testruns)
-                     .where(submissions: {user_id: current_user.id, user_type: current_user.class.name})
-                     .order('testruns.created_at DESC').first
+      .where(submissions: {user_id: current_user.id, user_type: current_user.class.name})
+      .order('testruns.created_at DESC').first
 
     # Return if no submission was found
     if submission.blank? || @embed_options[:disable_hints] || @embed_options[:hide_test_results]
@@ -26,8 +27,8 @@ class FlowrController < ApplicationController
       end
       # once the programming language model becomes available, the language name can be added to the query to
       # produce more relevant results
-      query = attributes.map{|att| att.value}.join(' ')
-      { submission: submission, error: error, attributes: attributes, query: query }
+      query = attributes.map(&:value).join(' ')
+      {submission: submission, error: error, attributes: attributes, query: query}
     end
 
     # Always return JSON
diff --git a/app/controllers/internal_users_controller.rb b/app/controllers/internal_users_controller.rb
index 90c390e1..c57de79f 100644
--- a/app/controllers/internal_users_controller.rb
+++ b/app/controllers/internal_users_controller.rb
@@ -93,7 +93,8 @@ class InternalUsersController < ApplicationController
   private :require_reset_password_token
 
   def require_token(type)
-    @user = InternalUser.send(:"load_from_#{type}_token", params[:token] || params[:internal_user].try(:[], :"#{type}_token"))
+    @user = InternalUser.send(:"load_from_#{type}_token",
+      params[:token] || params[:internal_user].try(:[], :"#{type}_token"))
     render_not_authorized unless @user
   end
   private :require_token
diff --git a/app/controllers/proxy_exercises_controller.rb b/app/controllers/proxy_exercises_controller.rb
index b5c7eccd..565e6079 100644
--- a/app/controllers/proxy_exercises_controller.rb
+++ b/app/controllers/proxy_exercises_controller.rb
@@ -1,7 +1,9 @@
+# frozen_string_literal: true
+
 class ProxyExercisesController < ApplicationController
   include CommonBehavior
 
-  before_action :set_exercise_and_authorize, only: MEMBER_ACTIONS + [:clone, :reload]
+  before_action :set_exercise_and_authorize, only: MEMBER_ACTIONS + %i[clone reload]
 
   def authorize!
     authorize(@proxy_exercise || @proxy_exercises)
@@ -9,10 +11,11 @@ class ProxyExercisesController < ApplicationController
   private :authorize!
 
   def clone
-    proxy_exercise = @proxy_exercise.duplicate(public: false, token: nil, exercises: @proxy_exercise.exercises, user: current_user)
+    proxy_exercise = @proxy_exercise.duplicate(public: false, token: nil, exercises: @proxy_exercise.exercises,
+user: current_user)
     proxy_exercise.send(:generate_token)
     if proxy_exercise.save
-      redirect_to(proxy_exercise, notice: t('shared.object_cloned', model:  ProxyExercise.model_name.human))
+      redirect_to(proxy_exercise, notice: t('shared.object_cloned', model: ProxyExercise.model_name.human))
     else
       flash[:danger] = t('shared.message_failure')
       redirect_to(@proxy_exercise)
@@ -21,7 +24,7 @@ class ProxyExercisesController < ApplicationController
 
   def create
     myparams = proxy_exercise_params
-    myparams[:exercises] = Exercise.find(myparams[:exercise_ids].reject { |c| c.empty? })
+    myparams[:exercises] = Exercise.find(myparams[:exercise_ids].reject(&:empty?))
     @proxy_exercise = ProxyExercise.new(myparams)
     authorize!
 
@@ -39,7 +42,10 @@ class ProxyExercisesController < ApplicationController
   end
 
   def proxy_exercise_params
-    params[:proxy_exercise].permit(:description, :title, :public, :exercise_ids  => []).merge(user_id: current_user.id, user_type: current_user.class.name) if params[:proxy_exercise].present?
+    if params[:proxy_exercise].present?
+      params[:proxy_exercise].permit(:description, :title, :public, exercise_ids: []).merge(user_id: current_user.id,
+user_type: current_user.class.name)
+    end
   end
   private :proxy_exercise_params
 
@@ -50,7 +56,7 @@ class ProxyExercisesController < ApplicationController
   end
 
   def new
-    @proxy_exercise =  ProxyExercise.new
+    @proxy_exercise = ProxyExercise.new
     @search = policy_scope(Exercise).ransack(params[:q])
     @exercises = @search.result.order(:title)
     authorize!
@@ -64,17 +70,15 @@ class ProxyExercisesController < ApplicationController
 
   def show
     @search = @proxy_exercise.exercises.ransack
-    @exercises = @proxy_exercise.exercises.ransack.result.order(:title) #@search.result.order(:title)
+    @exercises = @proxy_exercise.exercises.ransack.result.order(:title) # @search.result.order(:title)
   end
 
-  #we might want to think about auth here
-  def reload
-  end
+  # we might want to think about auth here
+  def reload; end
 
   def update
     myparams = proxy_exercise_params
-    myparams[:exercises] = Exercise.find(myparams[:exercise_ids].reject { |c| c.blank? })
+    myparams[:exercises] = Exercise.find(myparams[:exercise_ids].reject(&:blank?))
     update_and_respond(object: @proxy_exercise, params: myparams)
   end
-
 end
diff --git a/app/controllers/remote_evaluation_controller.rb b/app/controllers/remote_evaluation_controller.rb
index 4c35c2aa..2dd3bee7 100644
--- a/app/controllers/remote_evaluation_controller.rb
+++ b/app/controllers/remote_evaluation_controller.rb
@@ -26,7 +26,7 @@ class RemoteEvaluationController < ApplicationController
     if @submission.present?
       score_achieved_percentage = @submission.normalized_score
       result = try_lti
-      result.merge!({score: score_achieved_percentage * 100}) unless result[:score]
+      result[:score] = score_achieved_percentage * 100 unless result[:score]
       status = result[:status]
     end
 
@@ -38,7 +38,9 @@ class RemoteEvaluationController < ApplicationController
       lti_response = send_score(@submission)
       process_lti_response(lti_response)
     else
-      {message: "Your submission was successfully scored with #{@submission.normalized_score}%. However, your score could not be sent to the e-Learning platform. Please reopen the exercise through the e-Learning platform and try again.", status: 410}
+      {
+        message: "Your submission was successfully scored with #{@submission.normalized_score}%. However, your score could not be sent to the e-Learning platform. Please reopen the exercise through the e-Learning platform and try again.", status: 410
+      }
     end
   end
   private :try_lti
@@ -48,7 +50,8 @@ class RemoteEvaluationController < ApplicationController
       # Score has been reduced due to the passed deadline
       {message: I18n.t('exercises.submit.too_late'), status: 207, score: lti_response[:score_sent] * 100}
     elsif lti_response[:status] == 'success'
-      {message: I18n.t('sessions.destroy_through_lti.success_with_outcome', consumer: @submission.user.consumer.name), status: 202}
+      {message: I18n.t('sessions.destroy_through_lti.success_with_outcome', consumer: @submission.user.consumer.name),
+status: 202}
     else
       {message: I18n.t('exercises.submit.failure'), status: 424}
     end
@@ -77,7 +80,8 @@ class RemoteEvaluationController < ApplicationController
     submission_params[:study_group_id] = remote_evaluation_mapping.study_group_id
     submission_params[:cause] = cause
     submission_params[:user_type] = remote_evaluation_mapping.user_type
-    submission_params[:files_attributes] = reject_illegal_file_attributes(remote_evaluation_mapping.exercise, files_attributes)
+    submission_params[:files_attributes] =
+      reject_illegal_file_attributes(remote_evaluation_mapping.exercise, files_attributes)
     submission_params
   end
   private :build_submission_params
diff --git a/app/controllers/request_for_comments_controller.rb b/app/controllers/request_for_comments_controller.rb
index 128a5690..9330f0e0 100644
--- a/app/controllers/request_for_comments_controller.rb
+++ b/app/controllers/request_for_comments_controller.rb
@@ -5,7 +5,8 @@ class RequestForCommentsController < ApplicationController
 
   before_action :require_user!
   before_action :set_request_for_comment, only: %i[show mark_as_solved set_thank_you_note]
-  before_action :set_study_group_grouping, only: %i[index get_my_comment_requests get_rfcs_with_my_comments get_rfcs_for_exercise]
+  before_action :set_study_group_grouping,
+    only: %i[index get_my_comment_requests get_rfcs_with_my_comments get_rfcs_for_exercise]
 
   def authorize!
     authorize(@request_for_comments || @request_for_comment)
@@ -16,15 +17,15 @@ class RequestForCommentsController < ApplicationController
   # GET /request_for_comments.json
   def index
     @search = RequestForComment
-              .last_per_user(2)
-              .with_last_activity
-              .ransack(params[:q])
+      .last_per_user(2)
+      .with_last_activity
+      .ransack(params[:q])
     @request_for_comments = @search.result
-                                .joins(:exercise)
-                                .where(exercises: {unpublished: false})
-                                .includes(submission: [:study_group])
-                                .order('created_at DESC')
-                                .paginate(page: params[:page], total_entries: @search.result.length)
+      .joins(:exercise)
+      .where(exercises: {unpublished: false})
+      .includes(submission: [:study_group])
+      .order('created_at DESC')
+      .paginate(page: params[:page], total_entries: @search.result.length)
 
     authorize!
   end
@@ -32,12 +33,12 @@ class RequestForCommentsController < ApplicationController
   # GET /my_request_for_comments
   def get_my_comment_requests
     @search = RequestForComment
-              .with_last_activity
-              .where(user: current_user)
-              .ransack(params[:q])
+      .with_last_activity
+      .where(user: current_user)
+      .ransack(params[:q])
     @request_for_comments = @search.result
-                                   .order('created_at DESC')
-                                   .paginate(page: params[:page])
+      .order('created_at DESC')
+      .paginate(page: params[:page])
     authorize!
     render 'index'
   end
@@ -45,13 +46,13 @@ class RequestForCommentsController < ApplicationController
   # GET /my_rfc_activity
   def get_rfcs_with_my_comments
     @search = RequestForComment
-              .with_last_activity
-              .joins(:comments) # we don't need to outer join here, because we know the user has commented on these
-              .where(comments: {user_id: current_user.id})
-              .ransack(params[:q])
+      .with_last_activity
+      .joins(:comments) # we don't need to outer join here, because we know the user has commented on these
+      .where(comments: {user_id: current_user.id})
+      .ransack(params[:q])
     @request_for_comments = @search.result
-                                   .order('last_comment DESC')
-                                   .paginate(page: params[:page])
+      .order('last_comment DESC')
+      .paginate(page: params[:page])
     authorize!
     render 'index'
   end
@@ -60,13 +61,13 @@ class RequestForCommentsController < ApplicationController
   def get_rfcs_for_exercise
     exercise = Exercise.find(params[:exercise_id])
     @search = RequestForComment
-              .with_last_activity
-              .where(exercise_id: exercise.id)
-              .ransack(params[:q])
+      .with_last_activity
+      .where(exercise_id: exercise.id)
+      .ransack(params[:q])
     @request_for_comments = @search.result
-                                   .joins(:exercise)
-                                   .order('last_comment DESC')
-                                   .paginate(page: params[:page])
+      .joins(:exercise)
+      .order('last_comment DESC')
+      .paginate(page: params[:page])
     # let the exercise decide, whether its rfcs should be visible
     authorize(exercise)
     render 'index'
@@ -91,7 +92,7 @@ class RequestForCommentsController < ApplicationController
     @request_for_comment.thank_you_note = params[:note]
 
     commenters = @request_for_comment.commenters
-    commenters.each { |commenter| UserMailer.send_thank_you_note(@request_for_comment, commenter).deliver_now }
+    commenters.each {|commenter| UserMailer.send_thank_you_note(@request_for_comment, commenter).deliver_now }
 
     respond_to do |format|
       if @request_for_comment.save
@@ -143,14 +144,16 @@ class RequestForCommentsController < ApplicationController
   # Never trust parameters from the scary internet, only allow the white list through.
   def request_for_comment_params
     # The study_group_id might not be present in the session (e.g. for internal users), resulting in session[:study_group_id] = nil which is intended.
-    params.require(:request_for_comment).permit(:exercise_id, :file_id, :question, :requested_at, :solved, :submission_id).merge(user_id: current_user.id, user_type: current_user.class.name)
+    params.require(:request_for_comment).permit(:exercise_id, :file_id, :question, :requested_at, :solved, :submission_id).merge(
+user_id: current_user.id, user_type: current_user.class.name
+)
   end
 
   # The index page requires the grouping of the study groups
   # The study groups are grouped by the current study group and other study groups of the user
   def set_study_group_grouping
     current_study_group = StudyGroup.find_by(id: session[:study_group_id])
-    my_study_groups = current_user.study_groups.reject { |group| group == current_study_group }
+    my_study_groups = current_user.study_groups.reject {|group| group == current_study_group }
     @study_groups_grouping = [[t('request_for_comments.index.study_groups.current'), Array(current_study_group)],
                               [t('request_for_comments.index.study_groups.my'), my_study_groups]]
   end
diff --git a/app/controllers/sessions_controller.rb b/app/controllers/sessions_controller.rb
index 7cfe0e41..4a9b16c6 100644
--- a/app/controllers/sessions_controller.rb
+++ b/app/controllers/sessions_controller.rb
@@ -1,7 +1,10 @@
+# frozen_string_literal: true
+
 class SessionsController < ApplicationController
   include Lti
 
-  [:require_oauth_parameters, :require_valid_consumer_key, :require_valid_oauth_signature, :require_unique_oauth_nonce, :set_current_user, :require_valid_exercise_token, :set_study_group_membership, :set_embedding_options].each do |method_name|
+  %i[require_oauth_parameters require_valid_consumer_key require_valid_oauth_signature require_unique_oauth_nonce
+     set_current_user require_valid_exercise_token set_study_group_membership set_embedding_options].each do |method_name|
     before_action(method_name, only: :create_through_lti)
   end
 
@@ -24,8 +27,8 @@ class SessionsController < ApplicationController
       redirect_to(params[:custom_redirect_target])
     else
       redirect_to(implement_exercise_path(@exercise),
-                  notice: t("sessions.create_through_lti.session_#{lti_outcome_service?(@exercise.id, @current_user.id) ? 'with' : 'without'}_outcome",
-                  consumer: @consumer))
+        notice: t("sessions.create_through_lti.session_#{lti_outcome_service?(@exercise.id, @current_user.id) ? 'with' : 'without'}_outcome",
+          consumer: @consumer))
     end
   end
 
diff --git a/app/controllers/statistics_controller.rb b/app/controllers/statistics_controller.rb
index 00c969f0..48572463 100644
--- a/app/controllers/statistics_controller.rb
+++ b/app/controllers/statistics_controller.rb
@@ -1,8 +1,10 @@
+# frozen_string_literal: true
+
 class StatisticsController < ApplicationController
   include StatisticsHelper
 
-  before_action :authorize!, only: [:show, :graphs, :user_activity, :user_activity_history, :rfc_activity,
-                                    :rfc_activity_history]
+  before_action :authorize!, only: %i[show graphs user_activity user_activity_history rfc_activity
+                                      rfc_activity_history]
 
   def policy_class
     StatisticsPolicy
@@ -15,8 +17,7 @@ class StatisticsController < ApplicationController
     end
   end
 
-  def graphs
-  end
+  def graphs; end
 
   def user_activity
     respond_to do |format|
@@ -27,7 +28,7 @@ class StatisticsController < ApplicationController
   def user_activity_history
     respond_to do |format|
       format.html { render('activity_history', locals: {resource: :user}) }
-      format.json { render_ranged_data :ranged_user_data}
+      format.json { render_ranged_data :ranged_user_data }
     end
   end
 
@@ -46,14 +47,21 @@ class StatisticsController < ApplicationController
 
   def render_ranged_data(data_source)
     interval = params[:interval].to_s.empty? ? 'year' : params[:interval]
-    from = DateTime.strptime(params[:from], '%Y-%m-%d') rescue DateTime.new(0)
-    to = DateTime.strptime(params[:to], '%Y-%m-%d') rescue DateTime.now
-    render(json: self.send(data_source, interval, from, to))
+    from = begin
+      DateTime.strptime(params[:from], '%Y-%m-%d')
+    rescue StandardError
+      DateTime.new(0)
+    end
+    to = begin
+      DateTime.strptime(params[:to], '%Y-%m-%d')
+    rescue StandardError
+      DateTime.now
+    end
+    render(json: send(data_source, interval, from, to))
   end
 
   def authorize!
     authorize self
   end
   private :authorize!
-
 end
diff --git a/app/controllers/study_groups_controller.rb b/app/controllers/study_groups_controller.rb
index ce7a49f3..1bd3a4fa 100644
--- a/app/controllers/study_groups_controller.rb
+++ b/app/controllers/study_groups_controller.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class StudyGroupsController < ApplicationController
   include CommonBehavior
 
@@ -20,7 +22,8 @@ class StudyGroupsController < ApplicationController
 
   def update
     myparams = study_group_params
-    myparams[:external_users] = StudyGroupMembership.find(myparams[:study_group_membership_ids].reject(&:empty?)).map(&:user)
+    myparams[:external_users] =
+      StudyGroupMembership.find(myparams[:study_group_membership_ids].reject(&:empty?)).map(&:user)
     myparams.delete(:study_group_membership_ids)
     update_and_respond(object: @study_group, params: myparams)
   end
@@ -30,7 +33,7 @@ class StudyGroupsController < ApplicationController
   end
 
   def study_group_params
-    params[:study_group].permit(:id, :name, :study_group_membership_ids => []) if params[:study_group].present?
+    params[:study_group].permit(:id, :name, study_group_membership_ids: []) if params[:study_group].present?
   end
   private :study_group_params
 
@@ -44,5 +47,4 @@ class StudyGroupsController < ApplicationController
     authorize(@study_groups || @study_group)
   end
   private :authorize!
-
 end
diff --git a/app/controllers/submissions_controller.rb b/app/controllers/submissions_controller.rb
index 5b62c322..09c85239 100644
--- a/app/controllers/submissions_controller.rb
+++ b/app/controllers/submissions_controller.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class SubmissionsController < ApplicationController
   include ActionController::Live
   include CommonBehavior
@@ -6,15 +8,16 @@ class SubmissionsController < ApplicationController
   include SubmissionScoring
   include Tubesock::Hijack
 
-  before_action :set_submission, only: [:download, :download_file, :render_file, :run, :score, :extract_errors, :show, :statistics, :stop, :test]
-  before_action :set_docker_client, only: [:run, :test]
-  before_action :set_files, only: [:download, :download_file, :render_file, :show, :run]
-  before_action :set_file, only: [:download_file, :render_file, :run]
-  before_action :set_mime_type, only: [:download_file, :render_file]
-  skip_before_action :verify_authenticity_token, only: [:download_file, :render_file]
+  before_action :set_submission,
+    only: %i[download download_file render_file run score extract_errors show statistics stop test]
+  before_action :set_docker_client, only: %i[run test]
+  before_action :set_files, only: %i[download download_file render_file show run]
+  before_action :set_file, only: %i[download_file render_file run]
+  before_action :set_mime_type, only: %i[download_file render_file]
+  skip_before_action :verify_authenticity_token, only: %i[download_file render_file]
 
   def max_run_output_buffer_size
-    if(@submission.cause == 'requestComments')
+    if @submission.cause == 'requestComments'
       5000
     else
       500
@@ -34,30 +37,30 @@ class SubmissionsController < ApplicationController
   end
 
   def command_substitutions(filename)
-    {class_name: File.basename(filename, File.extname(filename)).camelize, filename: filename, module_name: File.basename(filename, File.extname(filename)).underscore}
+    {class_name: File.basename(filename, File.extname(filename)).camelize, filename: filename,
+module_name: File.basename(filename, File.extname(filename)).underscore}
   end
   private :command_substitutions
 
   def copy_comments
     # copy each annotation and set the target_file.id
-    unless(params[:annotations_arr].nil?)
-      params[:annotations_arr].each do | annotation |
-        #comment = Comment.new(annotation[1].permit(:user_id, :file_id, :user_type, :row, :column, :text, :created_at, :updated_at))
-        comment = Comment.new(:user_id => annotation[1][:user_id], :file_id => annotation[1][:file_id], :user_type => current_user.class.name, :row => annotation[1][:row], :column => annotation[1][:column], :text => annotation[1][:text])
-        source_file = CodeOcean::File.find(annotation[1][:file_id])
+    params[:annotations_arr]&.each do |annotation|
+      # comment = Comment.new(annotation[1].permit(:user_id, :file_id, :user_type, :row, :column, :text, :created_at, :updated_at))
+      comment = Comment.new(user_id: annotation[1][:user_id], file_id: annotation[1][:file_id],
+user_type: current_user.class.name, row: annotation[1][:row], column: annotation[1][:column], text: annotation[1][:text])
+      source_file = CodeOcean::File.find(annotation[1][:file_id])
 
-        # retrieve target file
-        target_file = @submission.files.detect do |file|
-          # file_id has to be that of a the former iteration OR of the initial file (if this is the first run)
-          file.file_id == source_file.file_id || file.file_id == source_file.id #seems to be needed here: (check this): || file.file_id == source_file.id ; yes this is needed, for comments on templates as well as comments on files added by users.
-        end
-
-        #save to assign an id
-        target_file.save!
-
-        comment.file_id = target_file.id
-        comment.save!
+      # retrieve target file
+      target_file = @submission.files.detect do |file|
+        # file_id has to be that of a the former iteration OR of the initial file (if this is the first run)
+        file.file_id == source_file.file_id || file.file_id == source_file.id # seems to be needed here: (check this): || file.file_id == source_file.id ; yes this is needed, for comments on templates as well as comments on files added by users.
       end
+
+      # save to assign an id
+      target_file.save!
+
+      comment.file_id = target_file.id
+      comment.save!
     end
   end
 
@@ -75,30 +78,35 @@ class SubmissionsController < ApplicationController
     require 'zip'
     stringio = Zip::OutputStream.write_buffer do |zio|
       @files.each do |file|
-        zio.put_next_entry(file.path.to_s == '' ? file.name_with_extension : File.join(file.path, file.name_with_extension))
-        zio.write(file.content.present? ? file.content : file.native_file.read)
+        zio.put_next_entry(if file.path.to_s == ''
+                             file.name_with_extension
+                           else
+                             File.join(file.path,
+                               file.name_with_extension)
+                           end)
+        zio.write(file.content.presence || file.native_file.read)
       end
 
       # zip exercise description
-      zio.put_next_entry(t('activerecord.models.exercise.one') + '.txt')
-      zio.write(@submission.exercise.title + "\r\n======================\r\n")
+      zio.put_next_entry("#{t('activerecord.models.exercise.one')}.txt")
+      zio.write("#{@submission.exercise.title}\r\n======================\r\n")
       zio.write(@submission.exercise.description)
 
       # zip .co file
-      zio.put_next_entry(".co")
-      zio.write(File.read id_file)
+      zio.put_next_entry('.co')
+      zio.write(File.read(id_file))
       File.delete(id_file) if File.exist?(id_file)
 
       # zip client scripts
       scripts_path = 'app/assets/remote_scripts'
       Dir.foreach(scripts_path) do |file|
-        next if file == '.' or file == '..'
-        zio.put_next_entry(File.join('.scripts', File.basename(file)))
-        zio.write(File.read File.join(scripts_path, file))
-      end
+        next if (file == '.') || (file == '..')
 
+        zio.put_next_entry(File.join('.scripts', File.basename(file)))
+        zio.write(File.read(File.join(scripts_path, file)))
+      end
     end
-    send_data(stringio.string, filename: @submission.exercise.title.tr(" ", "_") + ".zip")
+    send_data(stringio.string, filename: "#{@submission.exercise.title.tr(' ', '_')}.zip")
   end
 
   def download_file
@@ -128,7 +136,7 @@ class SubmissionsController < ApplicationController
   end
 
   def run
-    # TODO reimplement SSEs with websocket commands
+    # TODO: reimplement SSEs with websocket commands
     # with_server_sent_events do |server_sent_event|
     #   output = @docker_client.execute_run_command(@submission, sanitize_filename)
 
@@ -155,56 +163,54 @@ class SubmissionsController < ApplicationController
         end
       end
 
-
       # socket is the socket into the container, tubesock is the socket to the client
 
       # give the docker_client the tubesock object, so that it can send messages (timeout)
       @docker_client.tubesock = tubesock
 
-      container_request_time = Time.now
+      container_request_time = Time.zone.now
       result = @docker_client.execute_run_command(@submission, sanitize_filename)
       tubesock.send_data JSON.dump({'cmd' => 'status', 'status' => result[:status]})
-      @waiting_for_container_time = Time.now - container_request_time
+      @waiting_for_container_time = Time.zone.now - container_request_time
 
       if result[:status] == :container_running
         socket = result[:socket]
         command = result[:command]
 
         socket.on :message do |event|
-          Rails.logger.info( Time.now.getutc.to_s + ": Docker sending: " + event.data)
+          Rails.logger.info("#{Time.zone.now.getutc}: Docker sending: #{event.data}")
           handle_message(event.data, tubesock, result[:container])
         end
 
-        socket.on :close do |event|
+        socket.on :close do |_event|
           kill_socket(tubesock)
         end
 
         tubesock.onmessage do |data|
-          Rails.logger.info(Time.now.getutc.to_s + ": Client sending: " + data)
+          Rails.logger.info("#{Time.zone.now.getutc}: Client sending: #{data}")
           # Check whether the client send a JSON command and kill container
           # if the command is 'client_kill', send it to docker otherwise.
           begin
-
             parsed = JSON.parse(data) unless data == "\n"
-            if parsed.class == Hash && parsed['cmd'] == 'client_kill'
-              Rails.logger.debug("Client exited container.")
+            if parsed.instance_of?(Hash) && parsed['cmd'] == 'client_kill'
+              Rails.logger.debug('Client exited container.')
               @docker_client.kill_container(result[:container])
             else
               socket.send data
-              Rails.logger.debug('Sent the received client data to docker:' + data)
+              Rails.logger.debug("Sent the received client data to docker:#{data}")
             end
-          rescue JSON::ParserError => error
+          rescue JSON::ParserError => e
             socket.send data
-            Rails.logger.debug('Rescued parsing error, sent the received client data to docker:' + data)
+            Rails.logger.debug("Rescued parsing error, sent the received client data to docker:#{data}")
             Sentry.set_extras(data: data)
           end
         end
 
         # Send command after all listeners are attached.
         # Newline required to flush
-        @execution_request_time = Time.now
-        socket.send command + "\n"
-        Rails.logger.info('Sent command: ' + command.to_s)
+        @execution_request_time = Time.zone.now
+        socket.send "#{command}\n"
+        Rails.logger.info("Sent command: #{command}")
       else
         kill_socket(tubesock)
       end
@@ -212,7 +218,7 @@ class SubmissionsController < ApplicationController
   end
 
   def kill_socket(tubesock)
-    @container_execution_time = Time.now - @execution_request_time unless @execution_request_time.blank?
+    @container_execution_time = Time.zone.now - @execution_request_time if @execution_request_time.present?
     # search for errors and save them as StructuredError (for scoring runs see submission_scoring.rb)
     errors = extract_errors
     send_hints(tubesock, errors)
@@ -225,7 +231,7 @@ class SubmissionsController < ApplicationController
     if @run_output.blank? || @run_output&.strip == '{"cmd":"exit"}' || @run_output&.strip == 'timeout:'
       @raw_output ||= ''
       @run_output ||= ''
-      parse_message t('exercises.implement.no_output', timestamp: l(Time.now, format: :short)), 'stdout', tubesock
+      parse_message t('exercises.implement.no_output', timestamp: l(Time.zone.now, format: :short)), 'stdout', tubesock
     end
 
     # Hijacked connection needs to be notified correctly
@@ -237,25 +243,26 @@ class SubmissionsController < ApplicationController
     @raw_output ||= ''
     @run_output ||= ''
     # Handle special commands first
-    if /^#exit|{"cmd": "exit"}/.match(message)
-      # Just call exit_container on the docker_client.
-      # Do not call kill_socket for the websocket to the client here.
-      # @docker_client.exit_container closes the socket to the container,
-      # kill_socket is called in the "on close handler" of the websocket to the container
-      @docker_client.exit_container(container)
-    elsif /^#timeout/.match(message)
-      @run_output = 'timeout: ' + @run_output # add information that this run timed out to the buffer
-    else
-      # Filter out information about run_command, test_command, user or working directory
-      run_command = @submission.execution_environment.run_command % command_substitutions(sanitize_filename)
-      test_command = @submission.execution_environment.test_command % command_substitutions(sanitize_filename)
-      if test_command.blank?
-        # If no test command is set, use the run_command for the RegEx below. Otherwise, no output will be displayed!
-        test_command = run_command
-      end
-      unless /root@|:\/workspace|#{run_command}|#{test_command}|bash: cmd:canvasevent: command not found/.match(message)
-        parse_message(message, 'stdout', tubesock, container)
-      end
+    case message
+      when /^#exit|{"cmd": "exit"}/
+        # Just call exit_container on the docker_client.
+        # Do not call kill_socket for the websocket to the client here.
+        # @docker_client.exit_container closes the socket to the container,
+        # kill_socket is called in the "on close handler" of the websocket to the container
+        @docker_client.exit_container(container)
+      when /^#timeout/
+        @run_output = "timeout: #{@run_output}" # add information that this run timed out to the buffer
+      else
+        # Filter out information about run_command, test_command, user or working directory
+        run_command = @submission.execution_environment.run_command % command_substitutions(sanitize_filename)
+        test_command = @submission.execution_environment.test_command % command_substitutions(sanitize_filename)
+        if test_command.blank?
+          # If no test command is set, use the run_command for the RegEx below. Otherwise, no output will be displayed!
+          test_command = run_command
+        end
+        unless %r{root@|:/workspace|#{run_command}|#{test_command}|bash: cmd:canvasevent: command not found}.match?(message)
+          parse_message(message, 'stdout', tubesock, container)
+        end
     end
   end
 
@@ -263,58 +270,58 @@ class SubmissionsController < ApplicationController
     parsed = ''
     begin
       parsed = JSON.parse(message)
-      if parsed.class == Hash and parsed.key?('cmd')
+      if parsed.instance_of?(Hash) && parsed.key?('cmd')
         socket.send_data message
-        Rails.logger.info('parse_message sent: ' + message)
+        Rails.logger.info("parse_message sent: #{message}")
         @docker_client.exit_container(container) if container && parsed['cmd'] == 'exit'
       else
-        parsed = {'cmd'=>'write','stream'=>output_stream,'data'=>message}
+        parsed = {'cmd' => 'write', 'stream' => output_stream, 'data' => message}
         socket.send_data JSON.dump(parsed)
-        Rails.logger.info('parse_message sent: ' + JSON.dump(parsed))
+        Rails.logger.info("parse_message sent: #{JSON.dump(parsed)}")
       end
     rescue JSON::ParserError => e
       # Check wether the message contains multiple lines, if true try to parse each line
-      if recursive and message.include? "\n"
-        for part in message.split("\n")
-          self.parse_message(part,output_stream,socket, container, false)
+      if recursive && message.include?("\n")
+        message.split("\n").each do |part|
+          parse_message(part, output_stream, socket, container, false)
         end
       elsif message.include?('<img') || message.start_with?('{"cmd') || message.include?('"turtlebatch"')
-        #Rails.logger.info('img foung')
+        # Rails.logger.info('img foung')
         @buffering = true
         @buffer = ''
         @buffer += message
-        #Rails.logger.info('Starting to buffer')
-      elsif @buffering and message.include?('/>')
+        # Rails.logger.info('Starting to buffer')
+      elsif @buffering && message.include?('/>')
         @buffer += message
-        parsed = {'cmd'=>'write','stream'=>output_stream,'data'=>@buffer}
+        parsed = {'cmd' => 'write', 'stream' => output_stream, 'data' => @buffer}
         socket.send_data JSON.dump(parsed)
-        #socket.send_data @buffer
+        # socket.send_data @buffer
         @buffering = false
-        #Rails.logger.info('Sent complete buffer')
-      elsif @buffering and message.end_with?("}\r")
+        # Rails.logger.info('Sent complete buffer')
+      elsif @buffering && message.end_with?("}\r")
         @buffer += message
         socket.send_data @buffer
         @buffering = false
-        #Rails.logger.info('Sent complete buffer')
+        # Rails.logger.info('Sent complete buffer')
       elsif @buffering
         @buffer += message
-        #Rails.logger.info('Appending to buffer')
+        # Rails.logger.info('Appending to buffer')
       else
-        #Rails.logger.info('else')
-        parsed = {'cmd'=>'write','stream'=>output_stream,'data'=>message}
+        # Rails.logger.info('else')
+        parsed = {'cmd' => 'write', 'stream' => output_stream, 'data' => message}
         socket.send_data JSON.dump(parsed)
-        Rails.logger.info('parse_message sent: ' + JSON.dump(parsed))
+        Rails.logger.info("parse_message sent: #{JSON.dump(parsed)}")
       end
     ensure
-      @raw_output += parsed['data'].to_s if parsed.class == Hash and parsed.key? 'data'
+      @raw_output += parsed['data'].to_s if parsed.instance_of?(Hash) && parsed.key?('data')
       # save the data that was send to the run_output if there is enough space left. this will be persisted as a testrun with cause "run"
       @run_output += JSON.dump(parsed).to_s if @run_output.size <= max_run_output_buffer_size
     end
   end
 
   def save_run_output
-    unless @run_output.blank?
-      @run_output = @run_output[(0..max_run_output_buffer_size-1)] # trim the string to max_message_buffer_size chars
+    if @run_output.present?
+      @run_output = @run_output[(0..max_run_output_buffer_size - 1)] # trim the string to max_message_buffer_size chars
       Testrun.create(
         file: @file,
         cause: 'run',
@@ -328,7 +335,7 @@ class SubmissionsController < ApplicationController
 
   def extract_errors
     results = []
-    unless @raw_output.blank?
+    if @raw_output.present?
       @submission.exercise.execution_environment.error_templates.each do |template|
         pattern = Regexp.new(template.signature).freeze
         if pattern.match(@raw_output)
@@ -361,7 +368,7 @@ class SubmissionsController < ApplicationController
         tubesock.send_data JSON.dump(score_submission(@submission))
 
         # To enable hints when scoring a submission, uncomment the next line:
-        #send_hints(tubesock, StructuredError.where(submission: @submission))
+        # send_hints(tubesock, StructuredError.where(submission: @submission))
 
         tubesock.send_data JSON.dump({'cmd' => 'exit'})
       ensure
@@ -372,8 +379,9 @@ class SubmissionsController < ApplicationController
 
   def send_hints(tubesock, errors)
     return if @embed_options[:disable_hints]
-    errors = errors.to_a.uniq { |e| e.hint}
-    errors.each do | error |
+
+    errors = errors.to_a.uniq(&:hint)
+    errors.each do |error|
       tubesock.send_data JSON.dump({cmd: 'hint', hint: error.hint, description: error.error_template.description})
     end
   end
@@ -384,7 +392,7 @@ class SubmissionsController < ApplicationController
   private :set_docker_client
 
   def set_file
-    @file = @files.detect { |file| file.name_with_extension == sanitize_filename }
+    @file = @files.detect {|file| file.name_with_extension == sanitize_filename }
     head :not_found unless @file
   end
   private :set_file
@@ -406,11 +414,9 @@ class SubmissionsController < ApplicationController
   end
   private :set_submission
 
-  def show
-  end
+  def show; end
 
-  def statistics
-  end
+  def statistics; end
 
   def test
     hijack do |tubesock|
@@ -436,10 +442,10 @@ class SubmissionsController < ApplicationController
     server_sent_event.write(nil, event: 'start')
     yield(server_sent_event) if block_given?
     server_sent_event.write({code: 200}, event: 'close')
-  rescue => exception
-    Sentry.capture_exception(exception)
-    logger.error(exception.message)
-    logger.error(exception.backtrace.join("\n"))
+  rescue StandardError => e
+    Sentry.capture_exception(e)
+    logger.error(e.message)
+    logger.error(e.backtrace.join("\n"))
     server_sent_event.write({code: 500}, event: 'close')
   ensure
     server_sent_event.close
@@ -457,16 +463,16 @@ class SubmissionsController < ApplicationController
     )
 
     # create .co file
-    path = "tmp/" + user.id.to_s + ".co"
+    path = "tmp/#{user.id}.co"
     # parse validation token
     content = "#{remote_evaluation_mapping.validation_token}\n"
     # parse remote request url
     content += "#{request.base_url}/evaluate\n"
     @submission.files.each do |file|
       file_path = file.path.to_s == '' ? file.name_with_extension : File.join(file.path, file.name_with_extension)
-      content += "#{file_path}=#{file.file_id.to_s}\n"
+      content += "#{file_path}=#{file.file_id}\n"
     end
-    File.open(path, "w+") do |f|
+    File.open(path, 'w+') do |f|
       f.write(content)
     end
     path
diff --git a/app/controllers/subscriptions_controller.rb b/app/controllers/subscriptions_controller.rb
index f86431e2..508bdcd6 100644
--- a/app/controllers/subscriptions_controller.rb
+++ b/app/controllers/subscriptions_controller.rb
@@ -1,5 +1,6 @@
-class SubscriptionsController < ApplicationController
+# frozen_string_literal: true
 
+class SubscriptionsController < ApplicationController
   def authorize!
     authorize(@subscription || @subscriptions)
   end
@@ -21,28 +22,26 @@ class SubscriptionsController < ApplicationController
   # DELETE /subscriptions/1
   # DELETE /subscriptions/1.json
   def destroy
-    begin
-      @subscription = Subscription.find(params[:id])
-    rescue
-      skip_authorization
+    @subscription = Subscription.find(params[:id])
+  rescue StandardError
+    skip_authorization
+    respond_to do |format|
+      format.html { redirect_to request_for_comments_url, alert: t('subscriptions.subscription_not_existent') }
+      format.json { render json: {message: t('subscriptions.subscription_not_existent')}, status: :not_found }
+    end
+  else
+    authorize!
+    rfc = @subscription.try(:request_for_comment)
+    @subscription.deleted = true
+    if @subscription.save
       respond_to do |format|
-        format.html { redirect_to request_for_comments_url, alert: t('subscriptions.subscription_not_existent') }
-        format.json { render json: {message: t('subscriptions.subscription_not_existent')}, status: :not_found }
+        format.html { redirect_to request_for_comment_url(rfc), notice: t('subscriptions.successfully_unsubscribed') }
+        format.json { render json: {message: t('subscriptions.successfully_unsubscribed')}, status: :ok }
       end
     else
-      authorize!
-      rfc = @subscription.try(:request_for_comment)
-      @subscription.deleted = true
-      if @subscription.save
-        respond_to do |format|
-          format.html { redirect_to request_for_comment_url(rfc), notice: t('subscriptions.successfully_unsubscribed') }
-          format.json { render json: {message: t('subscriptions.successfully_unsubscribed')}, status: :ok}
-        end
-      else
-        respond_to do |format|
-          format.html { redirect_to request_for_comment_url(rfc), :flash => { :danger => t('shared.message_failure') } }
-          format.json { render json: {message: t('shared.message_failure')}, status: :internal_server_error}
-        end
+      respond_to do |format|
+        format.html { redirect_to request_for_comment_url(rfc), flash: {danger: t('shared.message_failure')} }
+        format.json { render json: {message: t('shared.message_failure')}, status: :internal_server_error }
       end
     end
   end
@@ -56,7 +55,10 @@ class SubscriptionsController < ApplicationController
   def subscription_params
     current_user_id = current_user.try(:id)
     current_user_class_name = current_user.try(:class).try(:name)
-    params[:subscription].permit(:request_for_comment_id, :subscription_type).merge(user_id: current_user_id, user_type: current_user_class_name, deleted: false) if params[:subscription].present?
+    if params[:subscription].present?
+      params[:subscription].permit(:request_for_comment_id, :subscription_type).merge(user_id: current_user_id,
+user_type: current_user_class_name, deleted: false)
+    end
   end
   private :subscription_params
 end
diff --git a/app/controllers/tags_controller.rb b/app/controllers/tags_controller.rb
index ac462653..5b95df11 100644
--- a/app/controllers/tags_controller.rb
+++ b/app/controllers/tags_controller.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class TagsController < ApplicationController
   include CommonBehavior
 
@@ -18,8 +20,7 @@ class TagsController < ApplicationController
     destroy_and_respond(object: @tag)
   end
 
-  def edit
-  end
+  def edit; end
 
   def tag_params
     params[:tag].permit(:name) if params[:tag].present?
@@ -42,8 +43,7 @@ class TagsController < ApplicationController
   end
   private :set_tag
 
-  def show
-  end
+  def show; end
 
   def update
     update_and_respond(object: @tag, params: tag_params)
diff --git a/app/controllers/tips_controller.rb b/app/controllers/tips_controller.rb
index 9fa5170c..7afb4baf 100644
--- a/app/controllers/tips_controller.rb
+++ b/app/controllers/tips_controller.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class TipsController < ApplicationController
   include CommonBehavior
 
@@ -19,15 +21,14 @@ class TipsController < ApplicationController
     destroy_and_respond(object: @tip)
   end
 
-  def edit
-  end
+  def edit; end
 
   def tip_params
-    return unless params[:tip].present?
+    return if params[:tip].blank?
 
     params[:tip]
       .permit(:title, :description, :example, :file_type_id)
-      .each { |_key, value| value.strip! unless value.is_a?(Array) }
+      .each {|_key, value| value.strip! unless value.is_a?(Array) }
       .merge(user_id: current_user.id, user_type: current_user.class.name)
   end
   private :tip_params
@@ -48,8 +49,7 @@ class TipsController < ApplicationController
   end
   private :set_tip
 
-  def show
-  end
+  def show; end
 
   def update
     update_and_respond(object: @tip, params: tip_params)
diff --git a/app/controllers/user_exercise_feedbacks_controller.rb b/app/controllers/user_exercise_feedbacks_controller.rb
index e2e8a941..a4545c45 100644
--- a/app/controllers/user_exercise_feedbacks_controller.rb
+++ b/app/controllers/user_exercise_feedbacks_controller.rb
@@ -28,10 +28,10 @@ class UserExerciseFeedbacksController < ApplicationController
     @exercise = Exercise.find(uef_params[:exercise_id])
     rfc = RequestForComment.unsolved.where(exercise_id: @exercise.id, user_id: current_user.id).first
     submission = begin
-                   current_user.submissions.where(exercise_id: @exercise.id).order('created_at DESC').first
-                 rescue StandardError
-                   nil
-                 end
+      current_user.submissions.where(exercise_id: @exercise.id).order('created_at DESC').first
+    rescue StandardError
+      nil
+    end
 
     if @exercise
       @uef = UserExerciseFeedback.find_or_initialize_by(user: current_user, exercise: @exercise)
@@ -74,10 +74,10 @@ class UserExerciseFeedbacksController < ApplicationController
 
   def update
     submission = begin
-                   current_user.submissions.where(exercise_id: @exercise.id).order('created_at DESC').first
-                 rescue StandardError
-                   nil
-                 end
+      current_user.submissions.where(exercise_id: @exercise.id).order('created_at DESC').first
+    rescue StandardError
+      nil
+    end
     rfc = RequestForComment.unsolved.where(exercise_id: @exercise.id, user_id: current_user.id).first
     authorize!
     if @exercise && validate_inputs(uef_params)
@@ -115,7 +115,7 @@ class UserExerciseFeedbacksController < ApplicationController
   end
 
   def uef_params
-    return unless params[:user_exercise_feedback].present?
+    return if params[:user_exercise_feedback].blank?
 
     exercise_id = if params[:user_exercise_feedback].nil?
                     params[:exercise_id]
@@ -126,8 +126,8 @@ class UserExerciseFeedbacksController < ApplicationController
     user_id = current_user.id
     user_type = current_user.class.name
     latest_submission = Submission
-                        .where(user_id: user_id, user_type: user_type, exercise_id: exercise_id)
-                        .order(created_at: :desc).first
+      .where(user_id: user_id, user_type: user_type, exercise_id: exercise_id)
+      .order(created_at: :desc).first
 
     params[:user_exercise_feedback]
       .permit(:feedback_text, :difficulty, :exercise_id, :user_estimated_worktime)
@@ -140,10 +140,8 @@ class UserExerciseFeedbacksController < ApplicationController
   def validate_inputs(uef_params)
     if uef_params[:difficulty].to_i.negative? || uef_params[:difficulty].to_i >= comment_presets.size
       false
-    elsif uef_params[:user_estimated_worktime].to_i.negative? || uef_params[:user_estimated_worktime].to_i >= time_presets.size
-      false
     else
-      true
+      !(uef_params[:user_estimated_worktime].to_i.negative? || uef_params[:user_estimated_worktime].to_i >= time_presets.size)
     end
   rescue StandardError
     false
diff --git a/app/helpers/action_cable_helper.rb b/app/helpers/action_cable_helper.rb
index 01fa00d9..d09c5e0e 100644
--- a/app/helpers/action_cable_helper.rb
+++ b/app/helpers/action_cable_helper.rb
@@ -1,15 +1,17 @@
 # frozen_string_literal: true
+
 module ActionCableHelper
   def trigger_rfc_action_cable
     Thread.new do
       # Context: RfC
       if submission.study_group_id.present?
         ActionCable.server.broadcast(
-            "la_exercises_#{exercise_id}_channel_study_group_#{submission.study_group_id}",
-            type: :rfc,
-            id: id,
-            html: ApplicationController.render(partial: 'request_for_comments/list_entry',
-                                               locals: {request_for_comment: self}))
+          "la_exercises_#{exercise_id}_channel_study_group_#{submission.study_group_id}",
+          type: :rfc,
+          id: id,
+          html: ApplicationController.render(partial: 'request_for_comments/list_entry',
+                                             locals: {request_for_comment: self})
+        )
       end
     ensure
       ActiveRecord::Base.connection_pool.release_connection
@@ -26,9 +28,10 @@ module ActionCableHelper
       # Context: Submission
       if study_group_id.present?
         ActionCable.server.broadcast(
-            "la_exercises_#{exercise_id}_channel_study_group_#{study_group_id}",
-            type: :working_times,
-            working_time_data: exercise.get_working_times_for_study_group(study_group_id, user))
+          "la_exercises_#{exercise_id}_channel_study_group_#{study_group_id}",
+          type: :working_times,
+          working_time_data: exercise.get_working_times_for_study_group(study_group_id, user)
+        )
       end
     ensure
       ActiveRecord::Base.connection_pool.release_connection
diff --git a/app/helpers/admin/dashboard_helper.rb b/app/helpers/admin/dashboard_helper.rb
index 4b84627a..791b430d 100644
--- a/app/helpers/admin/dashboard_helper.rb
+++ b/app/helpers/admin/dashboard_helper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Admin
   module DashboardHelper
     def dashboard_data
diff --git a/app/helpers/application_helper.rb b/app/helpers/application_helper.rb
index 20b89244..23439b01 100644
--- a/app/helpers/application_helper.rb
+++ b/app/helpers/application_helper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ApplicationHelper
   APPLICATION_NAME = 'CodeOcean'
 
@@ -7,8 +9,8 @@ module ApplicationHelper
 
   def code_tag(code, language = nil)
     if code.present?
-      content_tag(:pre) do
-        content_tag(:code, code, class: "language-#{language}")
+      tag.pre do
+        tag.code(code, class: "language-#{language}")
       end
     else
       empty
@@ -16,12 +18,12 @@ module ApplicationHelper
   end
 
   def empty
-    content_tag(:i, nil, class: 'empty fa fa-minus')
+    tag.i(nil, class: 'empty fa fa-minus')
   end
 
   def label_column(label)
-    content_tag(:div, class: 'col-sm-3') do
-      content_tag(:strong) do
+    tag.div(class: 'col-sm-3') do
+      tag.strong do
         I18n.translation_present?("activerecord.attributes.#{label}") ? t("activerecord.attributes.#{label}") : t(label)
       end
     end
@@ -29,12 +31,13 @@ module ApplicationHelper
   private :label_column
 
   def no
-    content_tag(:i, nil, class: 'fa fa-times')
+    tag.i(nil, class: 'fa fa-times')
   end
 
   def progress_bar(value)
-    content_tag(:div, class: value ? 'progress' : 'disabled progress') do
-      content_tag(:div, value ? "#{value}%" : '', :'aria-valuemax' => 100, :'aria-valuemin' => 0, :'aria-valuenow' => value, class: 'progress-bar progress-bar-striped', role: 'progressbar', style: "width: #{[value || 0, 100].min}%;")
+    tag.div(class: value ? 'progress' : 'disabled progress') do
+      tag.div(value ? "#{value}%" : '', 'aria-valuemax': 100, 'aria-valuemin': 0,
+'aria-valuenow': value, class: 'progress-bar progress-bar-striped', role: 'progressbar', style: "width: #{[value || 0, 100].min}%;")
     end
   end
 
@@ -43,7 +46,7 @@ module ApplicationHelper
   end
 
   def row(options = {}, &block)
-    content_tag(:div, class: 'attribute-row row') do
+    tag.div(class: 'attribute-row row') do
       label_column(options[:label]) + value_column(options[:value], &block)
     end
   end
@@ -61,13 +64,13 @@ module ApplicationHelper
   end
 
   def value_column(value)
-    content_tag(:div, class: 'col-sm-9') do
+    tag.div(class: 'col-sm-9') do
       block_given? ? yield : symbol_for(value)
     end
   end
   private :value_column
 
   def yes
-    content_tag(:i, nil, class: 'fa fa-check')
+    tag.i(nil, class: 'fa fa-check')
   end
 end
diff --git a/app/helpers/error_template_attributes_helper.rb b/app/helpers/error_template_attributes_helper.rb
index 9046f407..708ba2c4 100644
--- a/app/helpers/error_template_attributes_helper.rb
+++ b/app/helpers/error_template_attributes_helper.rb
@@ -1,2 +1,4 @@
+# frozen_string_literal: true
+
 module ErrorTemplateAttributesHelper
 end
diff --git a/app/helpers/error_templates_helper.rb b/app/helpers/error_templates_helper.rb
index f42cf302..99320810 100644
--- a/app/helpers/error_templates_helper.rb
+++ b/app/helpers/error_templates_helper.rb
@@ -1,2 +1,4 @@
+# frozen_string_literal: true
+
 module ErrorTemplatesHelper
 end
diff --git a/app/helpers/exercise_helper.rb b/app/helpers/exercise_helper.rb
index 190a18f3..26343917 100644
--- a/app/helpers/exercise_helper.rb
+++ b/app/helpers/exercise_helper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ExerciseHelper
   include LtiHelper
 
@@ -6,7 +8,7 @@ module ExerciseHelper
   end
 
   def qa_js_tag
-    javascript_include_tag qa_url + "/assets/qa_api.js"
+    javascript_include_tag "#{qa_url}/assets/qa_api.js"
   end
 
   def qa_url
@@ -15,8 +17,6 @@ module ExerciseHelper
 
     if enabled
       config.read[:code_pilot][:url]
-    else
-      return nil
     end
   end
 end
diff --git a/app/helpers/lti_helper.rb b/app/helpers/lti_helper.rb
index 9d2f56b5..a398a7ea 100644
--- a/app/helpers/lti_helper.rb
+++ b/app/helpers/lti_helper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'oauth/request_proxy/action_controller_request' # Rails 5 changed `Rack::Request` to `ActionDispatch::Request`
 
 module LtiHelper
diff --git a/app/helpers/pagedown_form_builder.rb b/app/helpers/pagedown_form_builder.rb
index d38407f2..6b1ec5c6 100644
--- a/app/helpers/pagedown_form_builder.rb
+++ b/app/helpers/pagedown_form_builder.rb
@@ -16,20 +16,19 @@ class PagedownFormBuilder < ActionView::Helpers::FormBuilder
   private
 
   def wmd_button_bar
-    @template.content_tag :div, nil, id: "wmd-button-bar-#{base_id}"
+    @template.tag.div(nil, id: "wmd-button-bar-#{base_id}")
   end
 
   def wmd_textarea
     @template.text_area @object_name, @attribute_name,
-                       **@input_html_options,
-                       class: 'form-control wmd-input',
-                       id: "wmd-input-#{base_id}"
+      **@input_html_options,
+      class: 'form-control wmd-input',
+      id: "wmd-input-#{base_id}"
   end
 
   def wmd_preview
-    @template.content_tag :div, nil,
-                         class: 'wmd-preview',
-                         id: "wmd-preview-#{base_id}"
+    @template.tag.div(nil, class: 'wmd-preview',
+                         id: "wmd-preview-#{base_id}")
   end
 
   def show_wmd_preview?
diff --git a/app/helpers/statistics_helper.rb b/app/helpers/statistics_helper.rb
index 76135219..57ddd57d 100644
--- a/app/helpers/statistics_helper.rb
+++ b/app/helpers/statistics_helper.rb
@@ -1,226 +1,231 @@
-module StatisticsHelper
+# frozen_string_literal: true
 
+module StatisticsHelper
   WORKING_TIME_DELTA_IN_SECONDS = 5.minutes
   WORKING_TIME_DELTA_IN_SQL_INTERVAL = "'0:05:00'" # yes, a string with quotes
 
   def statistics_data
     [
-        {
-            key: 'users',
-            name: t('statistics.sections.users'),
-            entries: user_statistics
-        },
-        {
-            key: 'exercises',
-            name: t('statistics.sections.exercises'),
-            entries: exercise_statistics
-        },
-        {
-            key: 'request_for_comments',
-            name: t('statistics.sections.request_for_comments'),
-            entries: rfc_statistics
-        }
+      {
+        key: 'users',
+          name: t('statistics.sections.users'),
+          entries: user_statistics,
+      },
+      {
+        key: 'exercises',
+          name: t('statistics.sections.exercises'),
+          entries: exercise_statistics,
+      },
+      {
+        key: 'request_for_comments',
+          name: t('statistics.sections.request_for_comments'),
+          entries: rfc_statistics,
+      },
     ]
   end
 
   def user_statistics
     [
-        {
-            key: 'internal_users',
-            name: t('activerecord.models.internal_user.other'),
-            data: InternalUser.count,
-            url: internal_users_path
-        },
-        {
-            key: 'external_users',
-            name: t('activerecord.models.external_user.other'),
-            data: ExternalUser.count,
-            url: external_users_path
-        },
-        {
-            key: 'currently_active',
-            name: t('statistics.entries.users.currently_active'),
-            data: ExternalUser.joins(:submissions)
-                      .where(['submissions.created_at >= ?', DateTime.now - 5.minutes])
-                      .distinct('external_users.id').count,
-            url: 'statistics/graphs'
-        }
+      {
+        key: 'internal_users',
+          name: t('activerecord.models.internal_user.other'),
+          data: InternalUser.count,
+          url: internal_users_path,
+      },
+      {
+        key: 'external_users',
+          name: t('activerecord.models.external_user.other'),
+          data: ExternalUser.count,
+          url: external_users_path,
+      },
+      {
+        key: 'currently_active',
+          name: t('statistics.entries.users.currently_active'),
+          data: ExternalUser.joins(:submissions)
+            .where(['submissions.created_at >= ?', DateTime.now - 5.minutes])
+            .distinct('external_users.id').count,
+          url: 'statistics/graphs',
+      },
     ]
   end
 
   def exercise_statistics
     [
-        {
-            key: 'exercises',
-            name: t('activerecord.models.exercise.other'),
-            data: Exercise.count,
-            url: exercises_path
-        },
-        {
-            key: 'average_submissions',
-            name: t('statistics.entries.exercises.average_number_of_submissions'),
-            data: (Submission.count.to_f / Exercise.count).round(2)
-        },
-        {
-            key: 'submissions_per_minute',
-            name: t('statistics.entries.exercises.submissions_per_minute'),
-            data: (Submission.where('created_at >= ?', DateTime.now - 1.hours).count.to_f / 60).round(2),
-            unit: '/min',
-            url: statistics_graphs_path
-        },
-        {
-            key: 'autosaves_per_minute',
-            name: t('statistics.entries.exercises.autosaves_per_minute'),
-            data: (Submission.where('created_at >= ?', DateTime.now - 1.hours).where(cause: 'autosave').count.to_f / 60).round(2),
-            unit: '/min'
-        },
-        {
-            key: 'container_requests_per_minute',
-            name: t('statistics.entries.exercises.container_requests_per_minute'),
-            data: (Testrun.where('created_at >= ?', DateTime.now - 1.hours).count.to_f / 60).round(2),
-            unit: '/min'
-        },
-        {
-            key: 'execution_environments',
-            name: t('activerecord.models.execution_environment.other'),
-            data: ExecutionEnvironment.count,
-            url: execution_environments_path
-        },
-        {
-            key: 'exercise_collections',
-            name: t('activerecord.models.exercise_collection.other'),
-            data: ExerciseCollection.count,
-            url: exercise_collections_path
-        }
+      {
+        key: 'exercises',
+          name: t('activerecord.models.exercise.other'),
+          data: Exercise.count,
+          url: exercises_path,
+      },
+      {
+        key: 'average_submissions',
+          name: t('statistics.entries.exercises.average_number_of_submissions'),
+          data: (Submission.count.to_f / Exercise.count).round(2),
+      },
+      {
+        key: 'submissions_per_minute',
+          name: t('statistics.entries.exercises.submissions_per_minute'),
+          data: (Submission.where('created_at >= ?', DateTime.now - 1.hour).count.to_f / 60).round(2),
+          unit: '/min',
+          url: statistics_graphs_path,
+      },
+      {
+        key: 'autosaves_per_minute',
+          name: t('statistics.entries.exercises.autosaves_per_minute'),
+          data: (Submission.where('created_at >= ?',
+            DateTime.now - 1.hour).where(cause: 'autosave').count.to_f / 60).round(2),
+          unit: '/min',
+      },
+      {
+        key: 'container_requests_per_minute',
+          name: t('statistics.entries.exercises.container_requests_per_minute'),
+          data: (Testrun.where('created_at >= ?', DateTime.now - 1.hour).count.to_f / 60).round(2),
+          unit: '/min',
+      },
+      {
+        key: 'execution_environments',
+          name: t('activerecord.models.execution_environment.other'),
+          data: ExecutionEnvironment.count,
+          url: execution_environments_path,
+      },
+      {
+        key: 'exercise_collections',
+          name: t('activerecord.models.exercise_collection.other'),
+          data: ExerciseCollection.count,
+          url: exercise_collections_path,
+      },
     ]
   end
 
   def rfc_statistics
     rfc_activity_data + [
-        {
-            key: 'comments',
-            name: t('activerecord.models.comment.other'),
-            data: Comment.count
-        }
+      {
+        key: 'comments',
+          name: t('activerecord.models.comment.other'),
+          data: Comment.count,
+      },
     ]
   end
 
   def user_activity_live_data
     [
-        {
-            key: 'active_in_last_hour',
-            name: t('statistics.entries.users.currently_active'),
-            data: ExternalUser.joins(:submissions)
-                      .where(['submissions.created_at >= ?', DateTime.now - 5.minutes])
-                      .distinct('external_users.id').count,
-        },
-        {
-            key: 'submissions_per_minute',
-            name: t('statistics.entries.exercises.submissions_per_minute'),
-            data: (Submission.where('created_at >= ?', DateTime.now - 1.hours).count.to_f / 60).round(2),
-            unit: '/min',
-            axis: 'right'
-        }
+      {
+        key: 'active_in_last_hour',
+          name: t('statistics.entries.users.currently_active'),
+          data: ExternalUser.joins(:submissions)
+            .where(['submissions.created_at >= ?', DateTime.now - 5.minutes])
+            .distinct('external_users.id').count,
+      },
+      {
+        key: 'submissions_per_minute',
+          name: t('statistics.entries.exercises.submissions_per_minute'),
+          data: (Submission.where('created_at >= ?', DateTime.now - 1.hour).count.to_f / 60).round(2),
+          unit: '/min',
+          axis: 'right',
+      },
     ]
   end
 
-  def rfc_activity_data(from=DateTime.new(0), to=DateTime.now)
+  def rfc_activity_data(from = DateTime.new(0), to = DateTime.now)
     [
-        {
-            key: 'rfcs',
-            name: t('activerecord.models.request_for_comment.other'),
-            data: RequestForComment.in_range(from, to).count,
-            url: request_for_comments_path
-        },
-        {
-            key: 'percent_solved',
-            name: t('statistics.entries.request_for_comments.percent_solved'),
-            data: (100.0 / RequestForComment.in_range(from, to).count * RequestForComment.in_range(from, to).where(solved: true).count).round(1),
-            unit: '%',
-            axis: 'right',
-            url: statistics_graphs_path
-        },
-        {
-            key: 'percent_soft_solved',
-            name: t('statistics.entries.request_for_comments.percent_soft_solved'),
-            data: (100.0 / RequestForComment.in_range(from, to).count * RequestForComment.in_range(from, to).unsolved.where(full_score_reached: true).count).round(1),
-            unit: '%',
-            axis: 'right',
-            url: statistics_graphs_path
-        },
-        {
-            key: 'percent_unsolved',
-            name: t('statistics.entries.request_for_comments.percent_unsolved'),
-            data: (100.0 / RequestForComment.in_range(from, to).count * RequestForComment.in_range(from, to).unsolved.count).round(1),
-            unit: '%',
-            axis: 'right',
-            url: statistics_graphs_path
-        },
-        {
-            key: 'rfcs_with_comments',
-            name: t('statistics.entries.request_for_comments.with_comments'),
-            data: RequestForComment.in_range(from, to).joins('join "submissions" s on s.id = request_for_comments.submission_id
+      {
+        key: 'rfcs',
+          name: t('activerecord.models.request_for_comment.other'),
+          data: RequestForComment.in_range(from, to).count,
+          url: request_for_comments_path,
+      },
+      {
+        key: 'percent_solved',
+          name: t('statistics.entries.request_for_comments.percent_solved'),
+          data: (100.0 / RequestForComment.in_range(from,
+            to).count * RequestForComment.in_range(from, to).where(solved: true).count).round(1),
+          unit: '%',
+          axis: 'right',
+          url: statistics_graphs_path,
+      },
+      {
+        key: 'percent_soft_solved',
+          name: t('statistics.entries.request_for_comments.percent_soft_solved'),
+          data: (100.0 / RequestForComment.in_range(from,
+            to).count * RequestForComment.in_range(from, to).unsolved.where(full_score_reached: true).count).round(1),
+          unit: '%',
+          axis: 'right',
+          url: statistics_graphs_path,
+      },
+      {
+        key: 'percent_unsolved',
+          name: t('statistics.entries.request_for_comments.percent_unsolved'),
+          data: (100.0 / RequestForComment.in_range(from,
+            to).count * RequestForComment.in_range(from, to).unsolved.count).round(1),
+          unit: '%',
+          axis: 'right',
+          url: statistics_graphs_path,
+      },
+      {
+        key: 'rfcs_with_comments',
+          name: t('statistics.entries.request_for_comments.with_comments'),
+          data: RequestForComment.in_range(from,
+            to).joins('join "submissions" s on s.id = request_for_comments.submission_id
                 join "files" f on f.context_id = s.id and f.context_type = \'Submission\'
                 join "comments" c on c.file_id = f.id').group('request_for_comments.id').count.size,
-            url: statistics_graphs_path
-        }
+          url: statistics_graphs_path,
+      },
     ]
   end
 
-  def ranged_rfc_data(interval='year', from=DateTime.new(0), to=DateTime.now)
+  def ranged_rfc_data(interval = 'year', from = DateTime.new(0), to = DateTime.now)
     [
-        {
-            key: 'rfcs',
-            name: t('activerecord.models.request_for_comment.other'),
-            data: RequestForComment.in_range(from, to)
-                      .select("date_trunc('#{interval}', created_at) AS \"key\", count(id) AS \"value\"")
-                      .group('key').order('key')
-        },
-        {
-            key: 'rfcs_solved',
-            name: t('statistics.entries.request_for_comments.percent_solved'),
-            data: RequestForComment.in_range(from, to)
-                      .where(solved: true)
-                      .select("date_trunc('#{interval}', created_at) AS \"key\", count(id) AS \"value\"")
-                      .group('key').order('key')
-        },
-        {
-            key: 'rfcs_soft_solved',
-            name: t('statistics.entries.request_for_comments.percent_soft_solved'),
-            data: RequestForComment.in_range(from, to).unsolved
-                      .where(full_score_reached: true)
-                      .select("date_trunc('#{interval}', created_at) AS \"key\", count(id) AS \"value\"")
-                      .group('key').order('key')
-        },
-        {
-            key: 'rfcs_unsolved',
-            name: t('statistics.entries.request_for_comments.percent_unsolved'),
-            data: RequestForComment.in_range(from, to).unsolved
-                      .select("date_trunc('#{interval}', created_at) AS \"key\", count(id) AS \"value\"")
-                      .group('key').order('key')
-        }
+      {
+        key: 'rfcs',
+          name: t('activerecord.models.request_for_comment.other'),
+          data: RequestForComment.in_range(from, to)
+            .select("date_trunc('#{interval}', created_at) AS \"key\", count(id) AS \"value\"")
+            .group('key').order('key'),
+      },
+      {
+        key: 'rfcs_solved',
+          name: t('statistics.entries.request_for_comments.percent_solved'),
+          data: RequestForComment.in_range(from, to)
+            .where(solved: true)
+            .select("date_trunc('#{interval}', created_at) AS \"key\", count(id) AS \"value\"")
+            .group('key').order('key'),
+      },
+      {
+        key: 'rfcs_soft_solved',
+          name: t('statistics.entries.request_for_comments.percent_soft_solved'),
+          data: RequestForComment.in_range(from, to).unsolved
+            .where(full_score_reached: true)
+            .select("date_trunc('#{interval}', created_at) AS \"key\", count(id) AS \"value\"")
+            .group('key').order('key'),
+      },
+      {
+        key: 'rfcs_unsolved',
+          name: t('statistics.entries.request_for_comments.percent_unsolved'),
+          data: RequestForComment.in_range(from, to).unsolved
+            .select("date_trunc('#{interval}', created_at) AS \"key\", count(id) AS \"value\"")
+            .group('key').order('key'),
+      },
     ]
   end
 
-  def ranged_user_data(interval='year', from=DateTime.new(0), to=DateTime.now)
+  def ranged_user_data(interval = 'year', from = DateTime.new(0), to = DateTime.now)
     [
-        {
-            key: 'active',
-            name: t('statistics.entries.users.active'),
-            data: ExternalUser.joins(:submissions)
-                      .where(submissions: {created_at: from..to})
-                      .select("date_trunc('#{interval}', submissions.created_at) AS \"key\", count(distinct external_users.id) AS \"value\"")
-                      .group('key').order('key')
-        },
-        {
-            key: 'submissions',
-            name: t('statistics.entries.exercises.submissions'),
-            data: Submission.where(created_at: from..to)
-                      .select("date_trunc('#{interval}', created_at) AS \"key\", count(id) AS \"value\"")
-                      .group('key').order('key'),
-            axis: 'right'
-        }
+      {
+        key: 'active',
+          name: t('statistics.entries.users.active'),
+          data: ExternalUser.joins(:submissions)
+            .where(submissions: {created_at: from..to})
+            .select("date_trunc('#{interval}', submissions.created_at) AS \"key\", count(distinct external_users.id) AS \"value\"")
+            .group('key').order('key'),
+      },
+      {
+        key: 'submissions',
+          name: t('statistics.entries.exercises.submissions'),
+          data: Submission.where(created_at: from..to)
+            .select("date_trunc('#{interval}', created_at) AS \"key\", count(id) AS \"value\"")
+            .group('key').order('key'),
+          axis: 'right',
+      },
     ]
   end
-
 end
diff --git a/app/helpers/time_helper.rb b/app/helpers/time_helper.rb
index ca93c0d8..6db718ba 100644
--- a/app/helpers/time_helper.rb
+++ b/app/helpers/time_helper.rb
@@ -1,5 +1,6 @@
-module TimeHelper
+# frozen_string_literal: true
 
+module TimeHelper
   # convert timestamps ('12:34:56.789') to seconds
   def time_to_f(timestamp)
     unless timestamp.nil?
@@ -11,7 +12,6 @@ module TimeHelper
 
   # given a delta in seconds, return a "Hours:Minutes:Seconds" representation
   def format_time_difference(delta)
-    Time.at(delta).utc.strftime("%H:%M:%S")
+    Time.at(delta).utc.strftime('%H:%M:%S')
   end
-
 end
diff --git a/app/mailers/user_mailer.rb b/app/mailers/user_mailer.rb
index 1f88c014..13c9c250 100644
--- a/app/mailers/user_mailer.rb
+++ b/app/mailers/user_mailer.rb
@@ -1,8 +1,9 @@
-class UserMailer < ActionMailer::Base
+# frozen_string_literal: true
 
+class UserMailer < ApplicationMailer
   def mail(*args)
     # used to prevent the delivery to pseudonymous users without a valid email address
-    super unless args.first[:to].blank?
+    super if args.first[:to].present?
   end
 
   def activation_needed_email(user)
@@ -10,8 +11,7 @@ class UserMailer < ActionMailer::Base
     mail(subject: t('mailers.user_mailer.activation_needed.subject'), to: user.email)
   end
 
-  def activation_success_email(*)
-  end
+  def activation_success_email(*); end
 
   def reset_password_email(user)
     @reset_password_url = reset_password_internal_user_url(user, token: user.reset_password_token)
@@ -19,12 +19,15 @@ class UserMailer < ActionMailer::Base
   end
 
   def got_new_comment(comment, request_for_comment, commenting_user)
-    # todo: check whether we can take the last known locale of the receiver?
+    # TODO: check whether we can take the last known locale of the receiver?
     @receiver_displayname = request_for_comment.user.displayname
     @commenting_user_displayname = commenting_user.displayname
     @comment_text = comment.text
     @rfc_link = request_for_comment_url(request_for_comment)
-    mail(subject: t('mailers.user_mailer.got_new_comment.subject', commenting_user_displayname: @commenting_user_displayname), to: request_for_comment.user.email)
+    mail(
+subject: t('mailers.user_mailer.got_new_comment.subject',
+  commenting_user_displayname: @commenting_user_displayname), to: request_for_comment.user.email
+)
   end
 
   def got_new_comment_for_subscription(comment, subscription, from_user)
@@ -33,7 +36,10 @@ class UserMailer < ActionMailer::Base
     @comment_text = comment.text
     @rfc_link = request_for_comment_url(subscription.request_for_comment)
     @unsubscribe_link = unsubscribe_subscription_url(subscription)
-    mail(subject: t('mailers.user_mailer.got_new_comment_for_subscription.subject', author_displayname: @author_displayname), to: subscription.user.email)
+    mail(
+subject: t('mailers.user_mailer.got_new_comment_for_subscription.subject',
+  author_displayname: @author_displayname), to: subscription.user.email
+)
   end
 
   def send_thank_you_note(request_for_comments, receiver)
@@ -43,7 +49,7 @@ class UserMailer < ActionMailer::Base
     @rfc_link = request_for_comment_url(request_for_comments)
     mail(subject: t('mailers.user_mailer.send_thank_you_note.subject', author: @author), to: receiver.email)
   end
-  
+
   def exercise_anomaly_detected(exercise_collection, anomalies)
     @user = exercise_collection.user
     @receiver_displayname = exercise_collection.user.displayname
diff --git a/app/models/anomaly_notification.rb b/app/models/anomaly_notification.rb
index 8e9498fa..5bafbac9 100644
--- a/app/models/anomaly_notification.rb
+++ b/app/models/anomaly_notification.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AnomalyNotification < ApplicationRecord
   belongs_to :user, polymorphic: true
   belongs_to :exercise
diff --git a/app/models/code_ocean/file.rb b/app/models/code_ocean/file.rb
index 9c452200..205a37de 100644
--- a/app/models/code_ocean/file.rb
+++ b/app/models/code_ocean/file.rb
@@ -1,16 +1,15 @@
-require File.expand_path('../../../uploaders/file_uploader', __FILE__)
-require File.expand_path('../../../../lib/active_model/validations/boolean_presence_validator', __FILE__)
+# frozen_string_literal: true
+
+require File.expand_path('../../uploaders/file_uploader', __dir__)
+require File.expand_path('../../../lib/active_model/validations/boolean_presence_validator', __dir__)
 
 module CodeOcean
-
   class FileNameValidator < ActiveModel::Validator
     def validate(record)
       existing_files = File.where(name: record.name, path: record.path, file_type_id: record.file_type_id,
                                   context_id: record.context_id, context_type: record.context_type).to_a
-      unless existing_files.empty?
-        if (not record.context.is_a?(Exercise)) || (record.context.new_record?)
-          record.errors[:base] << 'Duplicate'
-        end
+      if !existing_files.empty? && (!record.context.is_a?(Exercise) || record.context.new_record?)
+        record.errors[:base] << 'Duplicate'
       end
     end
   end
@@ -19,7 +18,8 @@ module CodeOcean
     include DefaultValues
 
     DEFAULT_WEIGHT = 1.0
-    ROLES = %w[regular_file main_file reference_implementation executable_file teacher_defined_test user_defined_file user_defined_test teacher_defined_linter].freeze
+    ROLES = %w[regular_file main_file reference_implementation executable_file teacher_defined_test user_defined_file
+               user_defined_test teacher_defined_linter].freeze
     TEACHER_DEFINED_ROLES = ROLES - %w[user_defined_file]
 
     after_initialize :set_default_values
@@ -29,13 +29,13 @@ module CodeOcean
 
     belongs_to :context, polymorphic: true
     belongs_to :file, class_name: 'CodeOcean::File', optional: true # This is only required for submissions and is validated below
-    alias_method :ancestor, :file
+    alias ancestor file
     belongs_to :file_type
 
     has_many :files, class_name: 'CodeOcean::File'
     has_many :testruns
     has_many :comments
-    alias_method :descendants, :files
+    alias descendants files
 
     mount_uploader :native_file, FileUploader
 
@@ -61,7 +61,7 @@ module CodeOcean
     validates :weight, absence: true, unless: :teacher_defined_assessment?
     validates :file, presence: true if :context.is_a?(Submission)
 
-    validates_with FileNameValidator, fields: [:name, :path, :file_type_id]
+    validates_with FileNameValidator, fields: %i[name path file_type_id]
 
     ROLES.each do |role|
       define_method("#{role}?") { self.role == role }
@@ -94,7 +94,12 @@ module CodeOcean
     end
 
     def hash_content
-      self.hashed_content = Digest::MD5.new.hexdigest(file_type.try(:binary?) ? ::File.new(native_file.file.path, 'r').read : content)
+      self.hashed_content = Digest::MD5.new.hexdigest(if file_type.try(:binary?)
+                                                        ::File.new(native_file.file.path,
+                                                          'r').read
+                                                      else
+                                                        content
+                                                      end)
     end
     private :hash_content
 
@@ -108,7 +113,7 @@ module CodeOcean
     end
 
     def set_ancestor_values
-      [:feedback_message, :file_type_id, :hidden, :name, :path, :read_only, :role, :weight].each do |attribute|
+      %i[feedback_message file_type_id hidden name path read_only role weight].each do |attribute|
         send(:"#{attribute}=", ancestor.send(attribute))
       end
     end
diff --git a/app/models/codeharbor_link.rb b/app/models/codeharbor_link.rb
index b35dc6cf..b0403ef4 100644
--- a/app/models/codeharbor_link.rb
+++ b/app/models/codeharbor_link.rb
@@ -5,9 +5,7 @@ class CodeharborLink < ApplicationRecord
   validates :check_uuid_url, presence: true
   validates :api_key, presence: true
 
-  belongs_to :user, foreign_key: :user_id, class_name: 'InternalUser'
+  belongs_to :user, class_name: 'InternalUser'
 
-  def to_s
-    id.to_s
-  end
+  delegate :to_s, to: :id
 end
diff --git a/app/models/concerns/context.rb b/app/models/concerns/context.rb
index 18cadab7..6b47b065 100644
--- a/app/models/concerns/context.rb
+++ b/app/models/concerns/context.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Context
   extend ActiveSupport::Concern
 
diff --git a/app/models/concerns/creation.rb b/app/models/concerns/creation.rb
index f2070ff5..ec16164f 100644
--- a/app/models/concerns/creation.rb
+++ b/app/models/concerns/creation.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Creation
   extend ActiveSupport::Concern
 
diff --git a/app/models/concerns/default_values.rb b/app/models/concerns/default_values.rb
index e5c7f231..3fe789d4 100644
--- a/app/models/concerns/default_values.rb
+++ b/app/models/concerns/default_values.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module DefaultValues
   def set_default_values_if_present(options = {})
     options.each do |attribute, value|
diff --git a/app/models/consumer.rb b/app/models/consumer.rb
index dcb06c0c..691daeba 100644
--- a/app/models/consumer.rb
+++ b/app/models/consumer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Consumer < ApplicationRecord
   has_many :users
 
diff --git a/app/models/error_template.rb b/app/models/error_template.rb
index 83c2f360..f7624c12 100644
--- a/app/models/error_template.rb
+++ b/app/models/error_template.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ErrorTemplate < ApplicationRecord
   belongs_to :execution_environment
   has_and_belongs_to_many :error_template_attributes
diff --git a/app/models/error_template_attribute.rb b/app/models/error_template_attribute.rb
index 42661132..3a213e1e 100644
--- a/app/models/error_template_attribute.rb
+++ b/app/models/error_template_attribute.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ErrorTemplateAttribute < ApplicationRecord
   has_and_belongs_to_many :error_template
 
diff --git a/app/models/event.rb b/app/models/event.rb
index bab444df..52f3744a 100644
--- a/app/models/event.rb
+++ b/app/models/event.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Event < ApplicationRecord
   belongs_to :user, polymorphic: true
   belongs_to :exercise
diff --git a/app/models/execution_environment.rb b/app/models/execution_environment.rb
index 33d57868..e4d39a93 100644
--- a/app/models/execution_environment.rb
+++ b/app/models/execution_environment.rb
@@ -1,4 +1,6 @@
-require File.expand_path('../../../lib/active_model/validations/boolean_presence_validator', __FILE__)
+# frozen_string_literal: true
+
+require File.expand_path('../../lib/active_model/validations/boolean_presence_validator', __dir__)
 
 class ExecutionEnvironment < ApplicationRecord
   include Creation
@@ -17,7 +19,8 @@ class ExecutionEnvironment < ApplicationRecord
   validate :valid_test_setup?
   validate :working_docker_image?, if: :validate_docker_image?
   validates :docker_image, presence: true
-  validates :memory_limit, numericality: {greater_than_or_equal_to: DockerClient::MINIMUM_MEMORY_LIMIT, only_integer: true}, presence: true
+  validates :memory_limit,
+    numericality: {greater_than_or_equal_to: DockerClient::MINIMUM_MEMORY_LIMIT, only_integer: true}, presence: true
   validates :network_enabled, boolean_presence: true
   validates :name, presence: true
   validates :permitted_execution_time, numericality: {only_integer: true}, presence: true
@@ -35,7 +38,9 @@ class ExecutionEnvironment < ApplicationRecord
 
   def valid_test_setup?
     if test_command? ^ testing_framework?
-      errors.add(:test_command, I18n.t('activerecord.errors.messages.together', attribute: I18n.t('activerecord.attributes.execution_environment.testing_framework')))
+      errors.add(:test_command,
+        I18n.t('activerecord.errors.messages.together',
+          attribute: I18n.t('activerecord.attributes.execution_environment.testing_framework')))
     end
   end
   private :valid_test_setup?
@@ -46,11 +51,11 @@ class ExecutionEnvironment < ApplicationRecord
   private :validate_docker_image?
 
   def working_docker_image?
-    DockerClient.pull(docker_image) unless DockerClient.find_image_by_tag(docker_image).blank?
+    DockerClient.pull(docker_image) if DockerClient.find_image_by_tag(docker_image).present?
     output = DockerClient.new(execution_environment: self).execute_arbitrary_command(VALIDATION_COMMAND)
     errors.add(:docker_image, "error: #{output[:stderr]}") if output[:stderr].present?
-  rescue DockerClient::Error => error
-    errors.add(:docker_image, "error: #{error}")
+  rescue DockerClient::Error => e
+    errors.add(:docker_image, "error: #{e}")
   end
   private :working_docker_image?
 end
diff --git a/app/models/exercise.rb b/app/models/exercise.rb
index a06f4b13..369e403a 100644
--- a/app/models/exercise.rb
+++ b/app/models/exercise.rb
@@ -41,7 +41,7 @@ class Exercise < ApplicationRecord
   validates :unpublished, boolean_presence: true
   validates :title, presence: true
   validates :token, presence: true, uniqueness: true
-  validates_uniqueness_of :uuid, if: -> { uuid.present? }
+  validates :uuid, uniqueness: {if: -> { uuid.present? }}
 
   @working_time_statistics = nil
   attr_reader :working_time_statistics
@@ -57,10 +57,10 @@ class Exercise < ApplicationRecord
   end
 
   def finishers_percentage
-    if users.distinct.count != 0
-      (100.0 / users.distinct.count * finishers.count).round(2)
-    else
+    if users.distinct.count.zero?
       0
+    else
+      (100.0 / users.distinct.count * finishers.count).round(2)
     end
   end
 
@@ -73,11 +73,11 @@ class Exercise < ApplicationRecord
 
   def average_number_of_submissions
     user_count = internal_users.distinct.count + external_users.distinct.count
-    user_count == 0 ? 0 : submissions.count / user_count.to_f
+    user_count.zero? ? 0 : submissions.count / user_count.to_f
   end
 
   def time_maximum_score(user)
-    submissions.where(user: user).where("cause IN ('submit','assess')").where('score IS NOT NULL').order('score DESC, created_at ASC').first.created_at
+    submissions.where(user: user).where("cause IN ('submit','assess')").where.not(score: nil).order('score DESC, created_at ASC').first.created_at
   rescue StandardError
     Time.zone.at(0)
   end
@@ -107,7 +107,7 @@ class Exercise < ApplicationRecord
   end
 
   def study_group_working_time_query(exercise_id, study_group_id, additional_filter)
-    ''"
+    "
     WITH working_time_between_submissions AS (
       SELECT submissions.user_id,
          submissions.user_type,
@@ -200,7 +200,7 @@ class Exercise < ApplicationRecord
     FROM working_times_with_index
        JOIN internal_users ON user_type = 'InternalUser' AND user_id = internal_users.id
     ORDER BY index, score ASC;
-    "''
+    "
   end
 
   def get_working_times_for_study_group(study_group_id, user = nil)
@@ -217,7 +217,8 @@ class Exercise < ApplicationRecord
 
     results = ActiveRecord::Base.transaction do
       self.class.connection.execute("SET LOCAL intervalstyle = 'postgres'")
-      self.class.connection.execute(study_group_working_time_query(id, study_group_id, additional_filter)).each do |tuple|
+      self.class.connection.execute(study_group_working_time_query(id, study_group_id,
+        additional_filter)).each do |tuple|
         bucket = if maximum_score > 0.0 && tuple['score'] <= maximum_score
                    (tuple['score'] / maximum_score * max_bucket).round
                  else
@@ -230,11 +231,12 @@ class Exercise < ApplicationRecord
 
         user_progress[bucket][tuple['index']] = tuple['working_time_per_score']
         additional_user_data[bucket][tuple['index']] = {start_time: tuple['start_time'], score: tuple['score']}
-        additional_user_data[max_bucket + 1][tuple['index']] = {id: tuple['user_id'], type: tuple['user_type'], name: tuple['name']}
+        additional_user_data[max_bucket + 1][tuple['index']] =
+          {id: tuple['user_id'], type: tuple['user_type'], name: tuple['name']}
       end
     end
 
-    if results.ntuples > 0
+    if results.ntuples.positive?
       first_index = results[0]['index']
       last_index = results[results.ntuples - 1]['index']
       buckets = last_index - first_index
@@ -247,9 +249,9 @@ class Exercise < ApplicationRecord
   end
 
   def get_quantiles(quantiles)
-    quantiles_str = '[' + quantiles.join(',') + ']'
+    quantiles_str = "[#{quantiles.join(',')}]"
     result = ActiveRecord::Base.transaction do
-      self.class.connection.execute(''"
+      self.class.connection.execute("
       SET LOCAL intervalstyle = 'iso_8601';
             WITH working_time AS
       (
@@ -356,14 +358,14 @@ class Exercise < ApplicationRecord
                         exercise_id )
       SELECT   unnest(percentile_cont(array#{quantiles_str}) within GROUP (ORDER BY working_time))
       FROM     result
-      "'')
+      ")
     end
-    if result.count > 0
-      begin
-        quantiles.each_with_index.map { |_q, i| ActiveSupport::Duration.parse(result[i]['unnest']).to_f }
-      end
+    if result.count.positive?
+
+      quantiles.each_with_index.map {|_q, i| ActiveSupport::Duration.parse(result[i]['unnest']).to_f }
+
     else
-      quantiles.map { |_q| 0 }
+      quantiles.map {|_q| 0 }
     end
   end
 
@@ -380,11 +382,11 @@ class Exercise < ApplicationRecord
   def average_working_time
     ActiveRecord::Base.transaction do
       self.class.connection.execute("SET LOCAL intervalstyle = 'postgres'")
-      self.class.connection.execute(''"
+      self.class.connection.execute("
       SELECT avg(working_time) as average_time
       FROM
         (#{user_working_time_query}) AS baz;
-    "'').first['average_time']
+    ").first['average_time']
     end
   end
 
@@ -397,7 +399,7 @@ class Exercise < ApplicationRecord
     user_type = user.external_user? ? 'ExternalUser' : 'InternalUser'
     begin
       result = ActiveRecord::Base.transaction do
-        self.class.connection.execute(''"
+        self.class.connection.execute("
               SET LOCAL intervalstyle = 'iso_8601';
               WITH WORKING_TIME AS
               (SELECT user_id,
@@ -447,7 +449,7 @@ class Exercise < ApplicationRecord
                   SELECT e.external_id AS external_user_id, f.user_id, exercise_id, MAX(max_score) AS max_score, sum(working_time_new) AS working_time
                   FROM FILTERED_TIMES_UNTIL_MAX f, EXTERNAL_USERS e
                   WHERE f.user_id = e.id GROUP BY e.external_id, f.user_id, exercise_id
-          "'')
+          ")
       end
       ActiveSupport::Duration.parse(result.first['working_time']).to_f
     rescue StandardError
@@ -458,8 +460,8 @@ class Exercise < ApplicationRecord
   def duplicate(attributes = {})
     exercise = dup
     exercise.attributes = attributes
-    exercise_tags.each  { |et| exercise.exercise_tags << et.dup }
-    files.each { |file| exercise.files << file.dup }
+    exercise_tags.each  {|et| exercise.exercise_tags << et.dup }
+    files.each {|file| exercise.files << file.dup }
     exercise
   end
 
@@ -490,7 +492,7 @@ class Exercise < ApplicationRecord
     self.attributes = {
       title: task_node.xpath('p:meta-data/p:title/text()')[0].content,
       description: description,
-      instructions: description
+      instructions: description,
     }
     task_node.xpath('p:files/p:file').all? do |file|
       file_name_split = file.xpath('@filename').first.value.split('.')
@@ -498,16 +500,16 @@ class Exercise < ApplicationRecord
       role = determine_file_role_from_proforma_file(task_node, file)
       feedback_message_nodes = task_node.xpath('p:tests/p:test/p:test-configuration/c:feedback-message/text()')
       files.build({
-                    name: file_name_split.first,
+        name: file_name_split.first,
                     content: file.xpath('text()').first.content,
                     read_only: false,
                     hidden: file_class == 'internal',
                     role: role,
                     feedback_message: role == 'teacher_defined_test' ? feedback_message_nodes.first.content : nil,
-                    file_type: FileType.where(
+                    file_type: FileType.find_by(
                       file_extension: ".#{file_name_split.second}"
-                    ).take
-                  })
+                    ),
+      })
     end
     self.execution_environment_id = 1
   end
@@ -521,7 +523,7 @@ class Exercise < ApplicationRecord
     if user
       # FIXME: where(user: user) will not work here!
       begin
-        submissions.where(user: user).where("cause IN ('submit','assess')").where('score IS NOT NULL').order('score DESC').first.score || 0
+        submissions.where(user: user).where("cause IN ('submit','assess')").where.not(score: nil).order('score DESC').first.score || 0
       rescue StandardError
         0
       end
@@ -539,7 +541,8 @@ class Exercise < ApplicationRecord
   end
 
   def finishers
-    ExternalUser.joins(:submissions).where(submissions: {exercise_id: id, score: maximum_score, cause: %w[submit assess remoteSubmit remoteAssess]}).distinct
+    ExternalUser.joins(:submissions).where(submissions: {exercise_id: id, score: maximum_score,
+cause: %w[submit assess remoteSubmit remoteAssess]}).distinct
   end
 
   def set_default_values
@@ -552,18 +555,25 @@ class Exercise < ApplicationRecord
   end
 
   def valid_main_file?
-    errors.add(:files, I18n.t('activerecord.errors.models.exercise.at_most_one_main_file')) if files.main_files.count > 1
+    if files.main_files.count > 1
+      errors.add(:files,
+        I18n.t('activerecord.errors.models.exercise.at_most_one_main_file'))
+    end
   end
   private :valid_main_file?
 
   def valid_submission_deadlines?
     return unless submission_deadline.present? || late_submission_deadline.present?
 
-    errors.add(:late_submission_deadline, I18n.t('activerecord.errors.models.exercise.late_submission_deadline_not_alone')) if late_submission_deadline.present? && submission_deadline.blank?
+    if late_submission_deadline.present? && submission_deadline.blank?
+      errors.add(:late_submission_deadline,
+        I18n.t('activerecord.errors.models.exercise.late_submission_deadline_not_alone'))
+    end
 
     if submission_deadline.present? && late_submission_deadline.present? &&
        late_submission_deadline < submission_deadline
-      errors.add(:late_submission_deadline, I18n.t('activerecord.errors.models.exercise.late_submission_deadline_not_before_submission_deadline'))
+      errors.add(:late_submission_deadline,
+        I18n.t('activerecord.errors.models.exercise.late_submission_deadline_not_before_submission_deadline'))
     end
   end
   private :valid_submission_deadlines?
diff --git a/app/models/exercise_collection.rb b/app/models/exercise_collection.rb
index 98cc5a63..bc1e4fd9 100644
--- a/app/models/exercise_collection.rb
+++ b/app/models/exercise_collection.rb
@@ -1,15 +1,19 @@
+# frozen_string_literal: true
+
 class ExerciseCollection < ApplicationRecord
   include TimeHelper
 
   has_many :exercise_collection_items, dependent: :delete_all
-  alias_method :items, :exercise_collection_items
+  alias items exercise_collection_items
   has_many :exercises, through: :exercise_collection_items, inverse_of: :exercise_collections
   belongs_to :user, polymorphic: true
 
   def collection_statistics
     statistics = {}
     exercise_collection_items.each do |item|
-      statistics[item.position] = {exercise_id: item.exercise.id, exercise_title: item.exercise.title, working_time: time_to_f(item.exercise.average_working_time)}
+      statistics[item.position] =
+        {exercise_id: item.exercise.id, exercise_title: item.exercise.title,
+working_time: time_to_f(item.exercise.average_working_time)}
     end
     statistics
   end
@@ -18,8 +22,8 @@ class ExerciseCollection < ApplicationRecord
     if exercises.empty?
       0
     else
-      values = collection_statistics.values.reject { |o| o[:working_time].nil?}
-      sum = values.reduce(0) {|sum, item| sum + item[:working_time]}
+      values = collection_statistics.values.reject {|o| o[:working_time].nil? }
+      sum = values.reduce(0) {|sum, item| sum + item[:working_time] }
       sum / values.size
     end
   end
@@ -27,5 +31,4 @@ class ExerciseCollection < ApplicationRecord
   def to_s
     "#{I18n.t('activerecord.models.exercise_collection.one')}: #{name} (#{id})"
   end
-
 end
diff --git a/app/models/exercise_collection_item.rb b/app/models/exercise_collection_item.rb
index 6147c3a0..e4112bc7 100644
--- a/app/models/exercise_collection_item.rb
+++ b/app/models/exercise_collection_item.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ExerciseCollectionItem < ApplicationRecord
   belongs_to :exercise_collection
   belongs_to :exercise
diff --git a/app/models/exercise_tag.rb b/app/models/exercise_tag.rb
index 9ead6f13..4edff966 100644
--- a/app/models/exercise_tag.rb
+++ b/app/models/exercise_tag.rb
@@ -1,13 +1,14 @@
-class ExerciseTag < ApplicationRecord
+# frozen_string_literal: true
 
+class ExerciseTag < ApplicationRecord
   belongs_to :tag
   belongs_to :exercise
 
   before_save :destroy_if_empty_exercise_or_tag
 
   private
-  def destroy_if_empty_exercise_or_tag
-     destroy if exercise_id.blank? || tag_id.blank?
-  end
 
-end
\ No newline at end of file
+  def destroy_if_empty_exercise_or_tag
+    destroy if exercise_id.blank? || tag_id.blank?
+  end
+end
diff --git a/app/models/exercise_tip.rb b/app/models/exercise_tip.rb
index 20be149f..9d99abaa 100644
--- a/app/models/exercise_tip.rb
+++ b/app/models/exercise_tip.rb
@@ -13,6 +13,12 @@ class ExerciseTip < ApplicationRecord
 
   def tip_chain?
     # Ensure each referenced parent exercise tip is set for this exercise
-    errors.add :parent_exercise_tip, I18n.t('activerecord.errors.messages.together', attribute: I18n.t('activerecord.attributes.exercise_tip.tip')) unless ExerciseTip.exists?(exercise: exercise, id: parent_exercise_tip)
+    unless ExerciseTip.exists?(
+exercise: exercise, id: parent_exercise_tip
+)
+      errors.add :parent_exercise_tip,
+        I18n.t('activerecord.errors.messages.together',
+          attribute: I18n.t('activerecord.attributes.exercise_tip.tip'))
+    end
   end
 end
diff --git a/app/models/external_user.rb b/app/models/external_user.rb
index e19a269e..9081f850 100644
--- a/app/models/external_user.rb
+++ b/app/models/external_user.rb
@@ -1,13 +1,10 @@
-class ExternalUser < User
+# frozen_string_literal: true
 
+class ExternalUser < User
   validates :consumer_id, presence: true
   validates :external_id, presence: true
 
   def displayname
-    if name.blank?
-      "User " + id.to_s
-    else
-      name
-    end
+    name.presence || "User #{id}"
   end
 end
diff --git a/app/models/file_template.rb b/app/models/file_template.rb
index 2eba68be..794638b1 100644
--- a/app/models/file_template.rb
+++ b/app/models/file_template.rb
@@ -1,10 +1,9 @@
+# frozen_string_literal: true
+
 class FileTemplate < ApplicationRecord
-
   belongs_to :file_type
 
-
   def to_s
     name
   end
-
 end
diff --git a/app/models/file_type.rb b/app/models/file_type.rb
index cf128a62..a1d5a6e9 100644
--- a/app/models/file_type.rb
+++ b/app/models/file_type.rb
@@ -1,12 +1,14 @@
-require File.expand_path('../../../lib/active_model/validations/boolean_presence_validator', __FILE__)
+# frozen_string_literal: true
+
+require File.expand_path('../../lib/active_model/validations/boolean_presence_validator', __dir__)
 
 class FileType < ApplicationRecord
   include Creation
   include DefaultValues
 
-  AUDIO_FILE_EXTENSIONS = %w(.aac .flac .m4a .mp3 .ogg .wav .wma)
-  IMAGE_FILE_EXTENSIONS = %w(.bmp .gif .jpeg .jpg .png)
-  VIDEO_FILE_EXTENSIONS = %w(.avi .flv .mkv .mp4 .m4v .ogv .webm)
+  AUDIO_FILE_EXTENSIONS = %w[.aac .flac .m4a .mp3 .ogg .wav .wma].freeze
+  IMAGE_FILE_EXTENSIONS = %w[.bmp .gif .jpeg .jpg .png].freeze
+  VIDEO_FILE_EXTENSIONS = %w[.avi .flv .mkv .mp4 .m4v .ogv .webm].freeze
 
   after_initialize :set_default_values
 
@@ -21,7 +23,7 @@ class FileType < ApplicationRecord
   validates :name, presence: true
   validates :renderable, boolean_presence: true
 
-  [:audio, :image, :video].each do |type|
+  %i[audio image video].each do |type|
     define_method("#{type}?") do
       self.class.const_get("#{type.upcase}_FILE_EXTENSIONS").include?(file_extension)
     end
diff --git a/app/models/internal_user.rb b/app/models/internal_user.rb
index 9cef2cb4..bc848226 100644
--- a/app/models/internal_user.rb
+++ b/app/models/internal_user.rb
@@ -1,5 +1,6 @@
-class InternalUser < User
+# frozen_string_literal: true
 
+class InternalUser < User
   authenticates_with_sorcery!
 
   validates :email, presence: true, uniqueness: true
@@ -22,5 +23,4 @@ class InternalUser < User
   def displayname
     name
   end
-
 end
diff --git a/app/models/intervention.rb b/app/models/intervention.rb
index 43750626..39848f09 100644
--- a/app/models/intervention.rb
+++ b/app/models/intervention.rb
@@ -1,5 +1,6 @@
-class Intervention < ApplicationRecord
+# frozen_string_literal: true
 
+class Intervention < ApplicationRecord
   has_many :user_exercise_interventions
   has_many :users, through: :user_exercise_interventions, source_type: 'ExternalUser'
 
@@ -8,9 +9,8 @@ class Intervention < ApplicationRecord
   end
 
   def self.createDefaultInterventions
-    %w(BreakIntervention QuestionIntervention).each do |name|
+    %w[BreakIntervention QuestionIntervention].each do |name|
       Intervention.find_or_create_by(name: name)
     end
   end
-
-end
\ No newline at end of file
+end
diff --git a/app/models/lti_parameter.rb b/app/models/lti_parameter.rb
index ab92165f..fe39dc75 100644
--- a/app/models/lti_parameter.rb
+++ b/app/models/lti_parameter.rb
@@ -1,9 +1,11 @@
-class LtiParameter < ApplicationRecord
-  belongs_to :consumer, foreign_key: "consumers_id"
-  belongs_to :exercise, foreign_key: "exercises_id"
-  belongs_to :external_user, foreign_key: "external_users_id"
+# frozen_string_literal: true
 
-  scope :lis_outcome_service_url?, -> {
+class LtiParameter < ApplicationRecord
+  belongs_to :consumer, foreign_key: 'consumers_id'
+  belongs_to :exercise, foreign_key: 'exercises_id'
+  belongs_to :external_user, foreign_key: 'external_users_id'
+
+  scope :lis_outcome_service_url?, lambda {
     where("lti_parameters.lti_parameters ? 'lis_outcome_service_url'")
   }
-end
\ No newline at end of file
+end
diff --git a/app/models/proxy_exercise.rb b/app/models/proxy_exercise.rb
index 96c143b7..91835f96 100644
--- a/app/models/proxy_exercise.rb
+++ b/app/models/proxy_exercise.rb
@@ -1,236 +1,245 @@
+# frozen_string_literal: true
+
 class ProxyExercise < ApplicationRecord
-    include Creation
-    include DefaultValues
+  include Creation
+  include DefaultValues
 
-    after_initialize :generate_token
-    after_initialize :set_reason
-    after_initialize :set_default_values
+  after_initialize :generate_token
+  after_initialize :set_reason
+  after_initialize :set_default_values
 
-    has_and_belongs_to_many :exercises
-    has_many :user_proxy_exercise_exercises
+  has_and_belongs_to_many :exercises
+  has_many :user_proxy_exercise_exercises
 
-    validates :public, boolean_presence: true
+  validates :public, boolean_presence: true
 
-    def count_files
-        exercises.count
-    end
+  def count_files
+    exercises.count
+  end
 
-    def set_reason
-      @reason = {}
-    end
+  def set_reason
+    @reason = {}
+  end
 
-    def generate_token
-      self.token ||= SecureRandom.hex(4)
-    end
-    private :generate_token
+  def generate_token
+    self.token ||= SecureRandom.hex(4)
+  end
+  private :generate_token
 
-    def set_default_values
-      set_default_values_if_present(public: false)
-    end
-    private :set_default_values
+  def set_default_values
+    set_default_values_if_present(public: false)
+  end
+  private :set_default_values
 
-    def duplicate(attributes = {})
-      proxy_exercise = dup
-      proxy_exercise.attributes = attributes
-      proxy_exercise
-    end
+  def duplicate(attributes = {})
+    proxy_exercise = dup
+    proxy_exercise.attributes = attributes
+    proxy_exercise
+  end
 
-    def to_s
-      title
-    end
+  def to_s
+    title
+  end
 
-    def get_matching_exercise(user)
-      assigned_user_proxy_exercise = user_proxy_exercise_exercises.where(user: user).first
-      recommended_exercise =
-        if (assigned_user_proxy_exercise)
-          Rails.logger.debug("retrieved assigned exercise for user #{user.id}: Exercise #{assigned_user_proxy_exercise.exercise}" )
-          assigned_user_proxy_exercise.exercise
-        else
-          Rails.logger.debug("find new matching exercise for user #{user.id}" )
-          matching_exercise =
-              begin
-                find_matching_exercise(user)
-              rescue => e #fallback
-                Rails.logger.error("finding matching exercise failed. Fall back to random exercise! Error: #{$!}" )
-                @reason[:reason] = "fallback because of error"
-                @reason[:error] = "#{$!}:\n\t#{e.backtrace.join("\n\t")}"
-                exercises.where("expected_difficulty > 1").shuffle.first # difficulty should be > 1 to prevent dummy exercise from being chosen.
-              end
-          user.user_proxy_exercise_exercises << UserProxyExerciseExercise.create(user: user, exercise: matching_exercise, proxy_exercise: self, reason: @reason.to_json)
-          matching_exercise
+  def get_matching_exercise(user)
+    assigned_user_proxy_exercise = user_proxy_exercise_exercises.where(user: user).first
+    if assigned_user_proxy_exercise
+      Rails.logger.debug("retrieved assigned exercise for user #{user.id}: Exercise #{assigned_user_proxy_exercise.exercise}")
+      assigned_user_proxy_exercise.exercise
+    else
+      Rails.logger.debug("find new matching exercise for user #{user.id}")
+      matching_exercise =
+        begin
+          find_matching_exercise(user)
+        rescue StandardError => e # fallback
+          Rails.logger.error("finding matching exercise failed. Fall back to random exercise! Error: #{$ERROR_INFO}")
+          @reason[:reason] = 'fallback because of error'
+          @reason[:error] = "#{$ERROR_INFO}:\n\t#{e.backtrace.join("\n\t")}"
+          exercises.where('expected_difficulty > 1').sample # difficulty should be > 1 to prevent dummy exercise from being chosen.
         end
-      recommended_exercise
+      user.user_proxy_exercise_exercises << UserProxyExerciseExercise.create(user: user,
+exercise: matching_exercise, proxy_exercise: self, reason: @reason.to_json)
+      matching_exercise
     end
+  end
 
-    def find_matching_exercise(user)
-        exercises_user_has_accessed = user.submissions.where("cause IN ('submit','assess')").map{|s| s.exercise}.uniq.compact
-        tags_user_has_seen = exercises_user_has_accessed.map{|ex| ex.tags}.uniq.flatten
-        Rails.logger.debug("exercises_user_has_accessed #{exercises_user_has_accessed.map{|e|e.id}.join(",")}")
+  def find_matching_exercise(user)
+    exercises_user_has_accessed = user.submissions.where("cause IN ('submit','assess')").map(&:exercise).uniq.compact
+    tags_user_has_seen = exercises_user_has_accessed.map(&:tags).uniq.flatten
+    Rails.logger.debug("exercises_user_has_accessed #{exercises_user_has_accessed.map(&:id).join(',')}")
 
-        # find exercises
-        potential_recommended_exercises = []
-        exercises.where("expected_difficulty >= 1").each do |ex|
-          ## find exercises which have only tags the user has already seen
-          if (ex.tags - tags_user_has_seen).empty?
-            potential_recommended_exercises << ex
-          end
-        end
-        Rails.logger.debug("potential_recommended_exercises: #{potential_recommended_exercises.map{|e|e.id}}")
-        # if all exercises contain tags which the user has never seen, recommend easiest exercise
-        if potential_recommended_exercises.empty?
-          Rails.logger.debug("matched easiest exercise in pool")
-          @reason[:reason] = "easiest exercise in pool. empty potential exercises"
-          select_easiest_exercise(exercises)
-        else
-          select_best_matching_exercise(user, exercises_user_has_accessed, potential_recommended_exercises)
-        end
-    end
-    private :find_matching_exercise
-
-    def select_best_matching_exercise(user, exercises_user_has_accessed, potential_recommended_exercises)
-      topic_knowledge_user_and_max = get_user_knowledge_and_max_knowledge(user, exercises_user_has_accessed)
-      Rails.logger.debug("topic_knowledge_user_and_max: #{topic_knowledge_user_and_max}")
-      Rails.logger.debug("potential_recommended_exercises: #{potential_recommended_exercises.size}: #{potential_recommended_exercises.map{|p| p.id}}")
-      topic_knowledge_user = topic_knowledge_user_and_max[:user_topic_knowledge]
-      topic_knowledge_max = topic_knowledge_user_and_max[:max_topic_knowledge]
-      current_users_knowledge_lack = {}
-      topic_knowledge_max.keys.each do |tag|
-        current_users_knowledge_lack[tag] = topic_knowledge_user[tag] /  topic_knowledge_max[tag]
+    # find exercises
+    potential_recommended_exercises = []
+    exercises.where('expected_difficulty >= 1').find_each do |ex|
+      ## find exercises which have only tags the user has already seen
+      if (ex.tags - tags_user_has_seen).empty?
+        potential_recommended_exercises << ex
       end
+    end
+    Rails.logger.debug("potential_recommended_exercises: #{potential_recommended_exercises.map(&:id)}")
+    # if all exercises contain tags which the user has never seen, recommend easiest exercise
+    if potential_recommended_exercises.empty?
+      Rails.logger.debug('matched easiest exercise in pool')
+      @reason[:reason] = 'easiest exercise in pool. empty potential exercises'
+      select_easiest_exercise(exercises)
+    else
+      select_best_matching_exercise(user, exercises_user_has_accessed, potential_recommended_exercises)
+    end
+  end
+  private :find_matching_exercise
 
-      relative_knowledge_improvement = {}
-      potential_recommended_exercises.each do |potex|
-        tags =  potex.tags
-        relative_knowledge_improvement[potex] = 0.0
-        Rails.logger.debug("review potential exercise #{potex.id}")
-        tags.each do |tag|
-          tag_ratio = potex.exercise_tags.where(tag: tag).first.factor.to_f / potex.exercise_tags.inject(0){|sum, et| sum += et.factor }.to_f
-          max_topic_knowledge_ratio = potex.expected_difficulty * tag_ratio
-          old_relative_loss_tag = topic_knowledge_user[tag] / topic_knowledge_max[tag]
-          new_relative_loss_tag = topic_knowledge_user[tag] / (topic_knowledge_max[tag] + max_topic_knowledge_ratio)
-          Rails.logger.debug("tag #{tag} old_relative_loss_tag #{old_relative_loss_tag}, new_relative_loss_tag #{new_relative_loss_tag}, tag_ratio #{tag_ratio}")
-          relative_knowledge_improvement[potex] += old_relative_loss_tag - new_relative_loss_tag
-        end
+  def select_best_matching_exercise(user, exercises_user_has_accessed, potential_recommended_exercises)
+    topic_knowledge_user_and_max = get_user_knowledge_and_max_knowledge(user, exercises_user_has_accessed)
+    Rails.logger.debug("topic_knowledge_user_and_max: #{topic_knowledge_user_and_max}")
+    Rails.logger.debug("potential_recommended_exercises: #{potential_recommended_exercises.size}: #{potential_recommended_exercises.map(&:id)}")
+    topic_knowledge_user = topic_knowledge_user_and_max[:user_topic_knowledge]
+    topic_knowledge_max = topic_knowledge_user_and_max[:max_topic_knowledge]
+    current_users_knowledge_lack = {}
+    topic_knowledge_max.each_key do |tag|
+      current_users_knowledge_lack[tag] = topic_knowledge_user[tag] / topic_knowledge_max[tag]
+    end
+
+    relative_knowledge_improvement = {}
+    potential_recommended_exercises.each do |potex|
+      tags = potex.tags
+      relative_knowledge_improvement[potex] = 0.0
+      Rails.logger.debug("review potential exercise #{potex.id}")
+      tags.each do |tag|
+        tag_ratio = potex.exercise_tags.where(tag: tag).first.factor.to_f / potex.exercise_tags.inject(0) do |sum, et|
+                                                                              sum += et.factor
+                                                                            end
+        max_topic_knowledge_ratio = potex.expected_difficulty * tag_ratio
+        old_relative_loss_tag = topic_knowledge_user[tag] / topic_knowledge_max[tag]
+        new_relative_loss_tag = topic_knowledge_user[tag] / (topic_knowledge_max[tag] + max_topic_knowledge_ratio)
+        Rails.logger.debug("tag #{tag} old_relative_loss_tag #{old_relative_loss_tag}, new_relative_loss_tag #{new_relative_loss_tag}, tag_ratio #{tag_ratio}")
+        relative_knowledge_improvement[potex] += old_relative_loss_tag - new_relative_loss_tag
       end
-
-      highest_difficulty_user_has_accessed =  exercises_user_has_accessed.map{|e| e.expected_difficulty}.sort.last || 0
-      best_matching_exercise = find_best_exercise(relative_knowledge_improvement, highest_difficulty_user_has_accessed)
-      @reason[:reason] = "best matching exercise"
-      @reason[:highest_difficulty_user_has_accessed] = highest_difficulty_user_has_accessed
-      @reason[:current_users_knowledge_lack] = current_users_knowledge_lack
-      @reason[:relative_knowledge_improvement] = relative_knowledge_improvement
-
-      Rails.logger.debug("current users knowledge loss: " + current_users_knowledge_lack.map{|k,v| "#{k} => #{v}"}.to_s)
-      Rails.logger.debug("relative improvements #{relative_knowledge_improvement.map{|k,v| k.id.to_s + ':' + v.to_s}}")
-      best_matching_exercise
     end
-    private :select_best_matching_exercise
 
-    def find_best_exercise(relative_knowledge_improvement, highest_difficulty_user_has_accessed)
-      Rails.logger.debug("select most appropiate exercise for user. his highest difficulty was #{highest_difficulty_user_has_accessed}")
-      sorted_exercises = relative_knowledge_improvement.sort_by{|k,v| v}.reverse
+    highest_difficulty_user_has_accessed = exercises_user_has_accessed.map(&:expected_difficulty).max || 0
+    best_matching_exercise = find_best_exercise(relative_knowledge_improvement, highest_difficulty_user_has_accessed)
+    @reason[:reason] = 'best matching exercise'
+    @reason[:highest_difficulty_user_has_accessed] = highest_difficulty_user_has_accessed
+    @reason[:current_users_knowledge_lack] = current_users_knowledge_lack
+    @reason[:relative_knowledge_improvement] = relative_knowledge_improvement
 
-      sorted_exercises.each do |ex,diff|
-        Rails.logger.debug("review exercise #{ex.id} diff: #{ex.expected_difficulty}")
-        if (ex.expected_difficulty - highest_difficulty_user_has_accessed) <= 1
-          Rails.logger.debug("matched exercise #{ex.id}")
-          return ex
-        else
-          Rails.logger.debug("exercise #{ex.id} is too difficult")
-        end
+    Rails.logger.debug('current users knowledge loss: ' + current_users_knowledge_lack.map do |k, v|
+                                                            "#{k} => #{v}"
+                                                          end.to_s)
+    Rails.logger.debug("relative improvements #{relative_knowledge_improvement.map {|k, v| "#{k.id}:#{v}" }}")
+    best_matching_exercise
+  end
+  private :select_best_matching_exercise
+
+  def find_best_exercise(relative_knowledge_improvement, highest_difficulty_user_has_accessed)
+    Rails.logger.debug("select most appropiate exercise for user. his highest difficulty was #{highest_difficulty_user_has_accessed}")
+    sorted_exercises = relative_knowledge_improvement.sort_by {|_k, v| v }.reverse
+
+    sorted_exercises.each do |ex, _diff|
+      Rails.logger.debug("review exercise #{ex.id} diff: #{ex.expected_difficulty}")
+      if (ex.expected_difficulty - highest_difficulty_user_has_accessed) <= 1
+        Rails.logger.debug("matched exercise #{ex.id}")
+        return ex
+      else
+        Rails.logger.debug("exercise #{ex.id} is too difficult")
       end
-      easiest_exercise = sorted_exercises.min_by{|k,v| v}.first
-      Rails.logger.debug("no match, select easiest exercise as fallback #{easiest_exercise.id}")
-      easiest_exercise
     end
-    private :find_best_exercise
+    easiest_exercise = sorted_exercises.min_by {|_k, v| v }.first
+    Rails.logger.debug("no match, select easiest exercise as fallback #{easiest_exercise.id}")
+    easiest_exercise
+  end
+  private :find_best_exercise
 
-    # [score][quantile]
-    def scoring_matrix
-      [
-          [0  ,0  ,0  ,0  ,0  ],
-          [0.2,0.2,0.2,0.2,0.1],
-          [0.5,0.5,0.4,0.4,0.3],
-          [0.6,0.6,0.5,0.5,0.4],
-          [1  ,1  ,0.9,0.8,0.7],
-      ]
+  # [score][quantile]
+  def scoring_matrix
+    [
+      [0, 0, 0, 0, 0],
+      [0.2, 0.2, 0.2, 0.2, 0.1],
+      [0.5, 0.5, 0.4, 0.4, 0.3],
+      [0.6, 0.6, 0.5, 0.5, 0.4],
+      [1, 1, 0.9, 0.8, 0.7],
+    ]
+  end
+
+  def scoring_matrix_quantiles
+    [0.2, 0.4, 0.6, 0.8]
+  end
+  private :scoring_matrix_quantiles
+
+  def score(user, ex)
+    max_score = ex.maximum_score.to_f
+    if max_score <= 0
+      Rails.logger.debug("scoring user #{user.id} for exercise #{ex.id}:  score: 0")
+      return 0.0
     end
-
-    def scoring_matrix_quantiles
-      [0.2,0.4,0.6,0.8]
+    points_ratio = ex.maximum_score(user) / max_score
+    if points_ratio == 0.0
+      Rails.logger.debug("scoring user #{user.id} for exercise #{ex.id}: points_ratio=#{points_ratio} score: 0")
+      return 0.0
+    elsif points_ratio > 1.0
+      points_ratio = 1.0 # The score of the exercise was adjusted and is now lower than it was
     end
-    private :scoring_matrix_quantiles
-
-    def score(user, ex)
-      max_score = ex.maximum_score.to_f
-      if max_score <= 0
-        Rails.logger.debug("scoring user #{user.id} for exercise #{ex.id}:  score: 0" )
-        return 0.0
+    points_ratio_index = ((scoring_matrix.size - 1) * points_ratio).to_i
+    working_time_user = ex.accumulated_working_time_for_only(user)
+    quantiles_working_time = ex.get_quantiles(scoring_matrix_quantiles)
+    quantile_index = quantiles_working_time.size
+    quantiles_working_time.each_with_index do |quantile_time, i|
+      if working_time_user <= quantile_time
+        quantile_index = i
+        break
       end
-      points_ratio = ex.maximum_score(user) / max_score
-      if points_ratio == 0.0
-        Rails.logger.debug("scoring user #{user.id} for exercise #{ex.id}: points_ratio=#{points_ratio} score: 0" )
-        return 0.0
-      elsif points_ratio > 1.0
-        points_ratio = 1.0 # The score of the exercise was adjusted and is now lower than it was
-      end
-      points_ratio_index = ((scoring_matrix.size - 1)  * points_ratio).to_i
-      working_time_user = ex.accumulated_working_time_for_only(user)
-      quantiles_working_time = ex.get_quantiles(scoring_matrix_quantiles)
-      quantile_index = quantiles_working_time.size
-      quantiles_working_time.each_with_index do |quantile_time, i|
-        if working_time_user <= quantile_time
-          quantile_index = i
-          break
-        end
-      end
-      Rails.logger.debug(
-          "scoring user #{user.id} exercise #{ex.id}: worktime #{working_time_user}, points: #{points_ratio}" \
-          "(index #{points_ratio_index}) quantiles #{quantiles_working_time} placed into quantile index #{quantile_index} " \
-          "score: #{scoring_matrix[points_ratio_index][quantile_index]}")
-      scoring_matrix[points_ratio_index][quantile_index]
     end
-    private :score
+    Rails.logger.debug(
+        "scoring user #{user.id} exercise #{ex.id}: worktime #{working_time_user}, points: #{points_ratio}" \
+        "(index #{points_ratio_index}) quantiles #{quantiles_working_time} placed into quantile index #{quantile_index} " \
+        "score: #{scoring_matrix[points_ratio_index][quantile_index]}"
+      )
+    scoring_matrix[points_ratio_index][quantile_index]
+  end
+  private :score
 
-    def get_user_knowledge_and_max_knowledge(user, exercises)
-      # initialize knowledge for each tag with 0
-      all_used_tags_with_count = {}
-      exercises.each do |ex|
-        ex.tags.each do |t|
-          all_used_tags_with_count[t] ||= 0
-          all_used_tags_with_count[t] += 1
-        end
+  def get_user_knowledge_and_max_knowledge(user, exercises)
+    # initialize knowledge for each tag with 0
+    all_used_tags_with_count = {}
+    exercises.each do |ex|
+      ex.tags.each do |t|
+        all_used_tags_with_count[t] ||= 0
+        all_used_tags_with_count[t] += 1
       end
-      tags_counter = all_used_tags_with_count.keys.map{|tag| [tag,0]}.to_h
-      topic_knowledge_loss_user = all_used_tags_with_count.keys.map{|t| [t, 0]}.to_h
-      topic_knowledge_max = all_used_tags_with_count.keys.map{|t| [t, 0]}.to_h
-      exercises_sorted = exercises.sort_by { |ex| ex.time_maximum_score(user)}
-      exercises_sorted.each do |ex|
-        Rails.logger.debug("exercise: #{ex.id}: #{ex}")
-        user_score_factor = score(user, ex)
-        ex.tags.each do |t|
-          tags_counter[t] += 1
-          tag_diminishing_return_factor = tag_diminishing_return_function(tags_counter[t], all_used_tags_with_count[t])
-          tag_ratio = ex.exercise_tags.where(tag: t).first.factor.to_f / ex.exercise_tags.inject(0){|sum, et| sum + et.factor }.to_f
-          Rails.logger.debug("tag: #{t}, factor: #{ex.exercise_tags.where(tag: t).first.factor}, sumall: #{ex.exercise_tags.inject(0){|sum, et| sum + et.factor }}")
-          Rails.logger.debug("tag #{t}, count #{tags_counter[t]}, max: #{all_used_tags_with_count[t]}, factor: #{tag_diminishing_return_factor}")
-          Rails.logger.debug("tag_ratio #{tag_ratio}")
-          topic_knowledge_ratio = ex.expected_difficulty * tag_ratio
-          Rails.logger.debug("topic_knowledge_ratio #{topic_knowledge_ratio}")
-          topic_knowledge_loss_user[t] += (1 - user_score_factor) * topic_knowledge_ratio * tag_diminishing_return_factor
-          topic_knowledge_max[t] += topic_knowledge_ratio * tag_diminishing_return_factor
-        end
+    end
+    tags_counter = all_used_tags_with_count.keys.index_with {|_tag| 0 }
+    topic_knowledge_loss_user = all_used_tags_with_count.keys.index_with {|_t| 0 }
+    topic_knowledge_max = all_used_tags_with_count.keys.index_with {|_t| 0 }
+    exercises_sorted = exercises.sort_by {|ex| ex.time_maximum_score(user) }
+    exercises_sorted.each do |ex|
+      Rails.logger.debug("exercise: #{ex.id}: #{ex}")
+      user_score_factor = score(user, ex)
+      ex.tags.each do |t|
+        tags_counter[t] += 1
+        tag_diminishing_return_factor = tag_diminishing_return_function(tags_counter[t], all_used_tags_with_count[t])
+        tag_ratio = ex.exercise_tags.where(tag: t).first.factor.to_f / ex.exercise_tags.inject(0) do |sum, et|
+                                                                         sum + et.factor
+                                                                       end
+        Rails.logger.debug("tag: #{t}, factor: #{ex.exercise_tags.where(tag: t).first.factor}, sumall: #{ex.exercise_tags.inject(0) do |sum, et|
+                                                                                                           sum + et.factor
+                                                                                                         end }")
+        Rails.logger.debug("tag #{t}, count #{tags_counter[t]}, max: #{all_used_tags_with_count[t]}, factor: #{tag_diminishing_return_factor}")
+        Rails.logger.debug("tag_ratio #{tag_ratio}")
+        topic_knowledge_ratio = ex.expected_difficulty * tag_ratio
+        Rails.logger.debug("topic_knowledge_ratio #{topic_knowledge_ratio}")
+        topic_knowledge_loss_user[t] += (1 - user_score_factor) * topic_knowledge_ratio * tag_diminishing_return_factor
+        topic_knowledge_max[t] += topic_knowledge_ratio * tag_diminishing_return_factor
       end
-      {user_topic_knowledge: topic_knowledge_loss_user, max_topic_knowledge: topic_knowledge_max}
     end
+    {user_topic_knowledge: topic_knowledge_loss_user, max_topic_knowledge: topic_knowledge_max}
+  end
 
-    def tag_diminishing_return_function(count_tag, total_count_tag)
-      total_count_tag += 1 # bonus exercise comes on top
-      1 / (1 + (Math::E**(-3 / (0.5 * total_count_tag) * (count_tag - 0.5 * total_count_tag))))
-    end
-
-    def select_easiest_exercise(exercises)
-      exercises.order(:expected_difficulty).first
-    end
+  def tag_diminishing_return_function(count_tag, total_count_tag)
+    total_count_tag += 1 # bonus exercise comes on top
+    1 / (1 + (Math::E**(-3 / (0.5 * total_count_tag) * (count_tag - 0.5 * total_count_tag))))
+  end
 
+  def select_easiest_exercise(exercises)
+    exercises.order(:expected_difficulty).first
+  end
 end
diff --git a/app/models/request_for_comment.rb b/app/models/request_for_comment.rb
index 6dfb1ae4..e671492e 100644
--- a/app/models/request_for_comment.rb
+++ b/app/models/request_for_comment.rb
@@ -18,7 +18,7 @@ class RequestForComment < ApplicationRecord
 
   scope :unsolved, -> { where(solved: [false, nil]) }
   scope :in_range, ->(from, to) { where(created_at: from..to) }
-  scope :with_comments, -> { select { |rfc| rfc.comments.any? } }
+  scope :with_comments, -> { select {|rfc| rfc.comments.any? } }
 
   # after_save :trigger_rfc_action_cable
 
@@ -44,7 +44,7 @@ class RequestForComment < ApplicationRecord
   end
 
   def comments_count
-    submission.files.map { |file| file.comments.size }.sum
+    submission.files.sum {|file| file.comments.size }
   end
 
   def commenters
diff --git a/app/models/search.rb b/app/models/search.rb
index bbb59e5b..06f34ba7 100644
--- a/app/models/search.rb
+++ b/app/models/search.rb
@@ -1,4 +1,6 @@
+# frozen_string_literal: true
+
 class Search < ApplicationRecord
   belongs_to :user, polymorphic: true
   belongs_to :exercise
-end
\ No newline at end of file
+end
diff --git a/app/models/structured_error.rb b/app/models/structured_error.rb
index 4d48b97c..46b5cb6e 100644
--- a/app/models/structured_error.rb
+++ b/app/models/structured_error.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class StructuredError < ApplicationRecord
   belongs_to :error_template
   belongs_to :submission
@@ -5,8 +7,8 @@ class StructuredError < ApplicationRecord
   has_many :structured_error_attributes
 
   def self.create_from_template(template, message_buffer, submission)
-    instance = self.create(error_template: template, submission: submission)
-    template.error_template_attributes.each do | attribute |
+    instance = create(error_template: template, submission: submission)
+    template.error_template_attributes.each do |attribute|
       StructuredErrorAttribute.create_from_template(attribute, instance, message_buffer)
     end
     instance
@@ -14,7 +16,7 @@ class StructuredError < ApplicationRecord
 
   def hint
     content = error_template.hint
-    structured_error_attributes.each do | attribute |
+    structured_error_attributes.each do |attribute|
       content.sub! "{{#{attribute.error_template_attribute.key}}}", attribute.value if attribute.match
     end
     content
diff --git a/app/models/structured_error_attribute.rb b/app/models/structured_error_attribute.rb
index f5f7615b..7bf97a66 100644
--- a/app/models/structured_error_attribute.rb
+++ b/app/models/structured_error_attribute.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class StructuredErrorAttribute < ApplicationRecord
   belongs_to :structured_error
   belongs_to :error_template_attribute
@@ -5,11 +7,10 @@ class StructuredErrorAttribute < ApplicationRecord
   def self.create_from_template(attribute, structured_error, message_buffer)
     value = nil
     result = message_buffer.match(attribute.regex)
-    if result != nil
-      if result.captures.size > 0
-        value = result.captures[0]
-      end
+    if !result.nil? && result.captures.size.positive?
+      value = result.captures[0]
     end
-    self.create(structured_error: structured_error, error_template_attribute: attribute, value: value, match: result != nil)
+    create(structured_error: structured_error, error_template_attribute: attribute, value: value,
+match: !result.nil?)
   end
 end
diff --git a/app/models/study_group_membership.rb b/app/models/study_group_membership.rb
index 1f7aad91..efb9683f 100644
--- a/app/models/study_group_membership.rb
+++ b/app/models/study_group_membership.rb
@@ -4,5 +4,5 @@ class StudyGroupMembership < ApplicationRecord
   belongs_to :user, polymorphic: true
   belongs_to :study_group
 
-  validates_uniqueness_of :user_id, :scope => [:user_type, :study_group_id]
+  validates :user_id, uniqueness: {scope: %i[user_type study_group_id]}
 end
diff --git a/app/models/submission.rb b/app/models/submission.rb
index 46c89ad1..accee1e8 100644
--- a/app/models/submission.rb
+++ b/app/models/submission.rb
@@ -1,9 +1,12 @@
+# frozen_string_literal: true
+
 class Submission < ApplicationRecord
   include Context
   include Creation
   include ActionCableHelper
 
-  CAUSES = %w(assess download file render run save submit test autosave requestComments remoteAssess remoteSubmit)
+  CAUSES = %w[assess download file render run save submit test autosave requestComments remoteAssess
+              remoteSubmit].freeze
   FILENAME_URL_PLACEHOLDER = '{filename}'
   MAX_COMMENTS_ON_RECOMMENDED_RFC = 5
   OLDEST_RFC_TO_SHOW = 6.months
@@ -15,17 +18,27 @@ class Submission < ApplicationRecord
   has_many :structured_errors
   has_many :comments, through: :files
 
-  belongs_to :external_users, -> { where(submissions: {user_type: 'ExternalUser'}).includes(:submissions) }, foreign_key: :user_id, class_name: 'ExternalUser', optional: true
-  belongs_to :internal_users, -> { where(submissions: {user_type: 'InternalUser'}).includes(:submissions) }, foreign_key: :user_id, class_name: 'InternalUser', optional: true
+  belongs_to :external_users, lambda {
+                                where(submissions: {user_type: 'ExternalUser'}).includes(:submissions)
+                              }, foreign_key: :user_id, class_name: 'ExternalUser', optional: true
+  belongs_to :internal_users, lambda {
+                                where(submissions: {user_type: 'InternalUser'}).includes(:submissions)
+                              }, foreign_key: :user_id, class_name: 'InternalUser', optional: true
 
   delegate :execution_environment, to: :exercise
 
   scope :final, -> { where(cause: %w[submit remoteSubmit]) }
   scope :intermediate, -> { where.not(cause: 'submit') }
 
-  scope :before_deadline, -> { joins(:exercise).where('submissions.updated_at <= exercises.submission_deadline OR exercises.submission_deadline IS NULL') }
-  scope :within_grace_period, -> { joins(:exercise).where('(submissions.updated_at > exercises.submission_deadline) AND (submissions.updated_at <= exercises.late_submission_deadline OR exercises.late_submission_deadline IS NULL)') }
-  scope :after_late_deadline, -> { joins(:exercise).where('submissions.updated_at > exercises.late_submission_deadline') }
+  scope :before_deadline, lambda {
+                            joins(:exercise).where('submissions.updated_at <= exercises.submission_deadline OR exercises.submission_deadline IS NULL')
+                          }
+  scope :within_grace_period, lambda {
+                                joins(:exercise).where('(submissions.updated_at > exercises.submission_deadline) AND (submissions.updated_at <= exercises.late_submission_deadline OR exercises.late_submission_deadline IS NULL)')
+                              }
+  scope :after_late_deadline, lambda {
+                                joins(:exercise).where('submissions.updated_at > exercises.late_submission_deadline')
+                              }
 
   scope :latest, -> { order(updated_at: :desc).first }
 
@@ -36,7 +49,6 @@ class Submission < ApplicationRecord
 
   # after_save :trigger_working_times_action_cable
 
-
   def build_files_hash(files, attribute)
     files.map(&attribute.to_proc).zip(files).to_h
   end
@@ -57,12 +69,12 @@ class Submission < ApplicationRecord
     # expects the full file path incl. file extension
     # Caution: There must be no unnecessary path prefix included.
     # Use `file.ext` rather than `./file.ext`
-    collect_files.detect { |file| file.filepath == file_path }
+    collect_files.detect {|file| file.filepath == file_path }
   end
 
   def normalized_score
     ::NewRelic::Agent.add_custom_attributes({unnormalized_score: score})
-    if !score.nil? && !exercise.maximum_score.nil? && (exercise.maximum_score > 0)
+    if !score.nil? && !exercise.maximum_score.nil? && exercise.maximum_score.positive?
       score / exercise.maximum_score
     else
       0
@@ -119,6 +131,8 @@ class Submission < ApplicationRecord
   end
 
   def unsolved_rfc
-    RequestForComment.unsolved.where(exercise_id: exercise).where.not(question: nil).where(created_at: OLDEST_RFC_TO_SHOW.ago..Time.current).order("RANDOM()").find { |rfc_element| ((rfc_element.comments_count < MAX_COMMENTS_ON_RECOMMENDED_RFC) && (!rfc_element.question.empty?)) }
+    RequestForComment.unsolved.where(exercise_id: exercise).where.not(question: nil).where(created_at: OLDEST_RFC_TO_SHOW.ago..Time.current).order('RANDOM()').find do |rfc_element|
+      ((rfc_element.comments_count < MAX_COMMENTS_ON_RECOMMENDED_RFC) && !rfc_element.question.empty?)
+    end
   end
 end
diff --git a/app/models/subscription.rb b/app/models/subscription.rb
index ed3f3a3e..ae9477ae 100644
--- a/app/models/subscription.rb
+++ b/app/models/subscription.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Subscription < ApplicationRecord
   belongs_to :user, polymorphic: true
   belongs_to :request_for_comment
diff --git a/app/models/tag.rb b/app/models/tag.rb
index b6de61bb..d3d9c86e 100644
--- a/app/models/tag.rb
+++ b/app/models/tag.rb
@@ -1,22 +1,22 @@
-class Tag < ApplicationRecord
+# frozen_string_literal: true
 
+class Tag < ApplicationRecord
   has_many :exercise_tags
   has_many :exercises, through: :exercise_tags
 
-  validates_uniqueness_of :name
+  validates :name, uniqueness: true
 
   def destroy
-    if (can_be_destroyed?)
+    if can_be_destroyed?
       super
     end
   end
 
   def can_be_destroyed?
-    !exercises.any?
+    exercises.none?
   end
 
   def to_s
     name
   end
-
-end
\ No newline at end of file
+end
diff --git a/app/models/testrun.rb b/app/models/testrun.rb
index 4d09d398..e8903e61 100644
--- a/app/models/testrun.rb
+++ b/app/models/testrun.rb
@@ -1,4 +1,6 @@
+# frozen_string_literal: true
+
 class Testrun < ApplicationRecord
-    belongs_to :file, class_name: 'CodeOcean::File', optional: true
-    belongs_to :submission
+  belongs_to :file, class_name: 'CodeOcean::File', optional: true
+  belongs_to :submission
 end
diff --git a/app/models/tip.rb b/app/models/tip.rb
index 85427f41..2b4e26fb 100644
--- a/app/models/tip.rb
+++ b/app/models/tip.rb
@@ -6,11 +6,16 @@ class Tip < ApplicationRecord
   has_many :exercise_tips
   has_many :exercises, through: :exercise_tips
   belongs_to :file_type, optional: true
-  validates_presence_of :file_type, if: :example?
+  validates :file_type, presence: {if: :example?}
   validate :content?
 
   def content?
-    errors.add :description, I18n.t('activerecord.errors.messages.at_least', attribute: I18n.t('activerecord.attributes.tip.example')) unless [description?, example?].include?(true)
+    unless [
+      description?, example?
+    ].include?(true)
+      errors.add :description,
+        I18n.t('activerecord.errors.messages.at_least', attribute: I18n.t('activerecord.attributes.tip.example'))
+    end
   end
 
   def to_s
diff --git a/app/models/user.rb b/app/models/user.rb
index 668aa845..835a1617 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -3,7 +3,7 @@
 class User < ApplicationRecord
   self.abstract_class = true
 
-  ROLES = %w(admin teacher learner)
+  ROLES = %w[admin teacher learner].freeze
 
   belongs_to :consumer
   has_many :study_group_memberships, as: :user
@@ -19,10 +19,11 @@ class User < ApplicationRecord
   has_one :codeharbor_link, dependent: :destroy
   accepts_nested_attributes_for :user_proxy_exercise_exercises
 
-
   scope :with_submissions, -> { where('id IN (SELECT user_id FROM submissions)') }
 
-  scope :in_study_group_of, ->(user) { joins(:study_group_memberships).where(study_group_memberships: {study_group_id: user.study_groups}) unless user.admin? }
+  scope :in_study_group_of, lambda {|user|
+                              joins(:study_group_memberships).where(study_group_memberships: {study_group_id: user.study_groups}) unless user.admin?
+                            }
 
   ROLES.each do |role|
     define_method("#{role}?") { try(:role) == role }
diff --git a/app/models/user_exercise_feedback.rb b/app/models/user_exercise_feedback.rb
index f236f0c0..79b9bf74 100644
--- a/app/models/user_exercise_feedback.rb
+++ b/app/models/user_exercise_feedback.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class UserExerciseFeedback < ApplicationRecord
   include Creation
 
@@ -5,17 +7,17 @@ class UserExerciseFeedback < ApplicationRecord
   belongs_to :submission, optional: true
   has_one :execution_environment, through: :exercise
 
-  validates :user_id, uniqueness: { scope: [:exercise_id, :user_type] }
+  validates :user_id, uniqueness: {scope: %i[exercise_id user_type]}
 
   scope :intermediate, -> { where.not(normalized_score: 1.00) }
   scope :final, -> { where(normalized_score: 1.00) }
 
   def to_s
-    "User Exercise Feedback"
+    'User Exercise Feedback'
   end
 
   def anomaly_notification
     AnomalyNotification.where({exercise_id: exercise.id, user_id: user_id, user_type: user_type})
-        .where("created_at < ?", created_at).order("created_at DESC").to_a.first
+      .where('created_at < ?', created_at).order('created_at DESC').to_a.first
   end
 end
diff --git a/app/models/user_exercise_intervention.rb b/app/models/user_exercise_intervention.rb
index b3008206..e246ae80 100644
--- a/app/models/user_exercise_intervention.rb
+++ b/app/models/user_exercise_intervention.rb
@@ -1,5 +1,6 @@
-class UserExerciseIntervention < ApplicationRecord
+# frozen_string_literal: true
 
+class UserExerciseIntervention < ApplicationRecord
   belongs_to :user, polymorphic: true
   belongs_to :intervention
   belongs_to :exercise
@@ -7,5 +8,4 @@ class UserExerciseIntervention < ApplicationRecord
   validates :user, presence: true
   validates :exercise, presence: true
   validates :intervention, presence: true
-
-end
\ No newline at end of file
+end
diff --git a/app/models/user_proxy_exercise_exercise.rb b/app/models/user_proxy_exercise_exercise.rb
index 8a0cbb5d..971d7e72 100644
--- a/app/models/user_proxy_exercise_exercise.rb
+++ b/app/models/user_proxy_exercise_exercise.rb
@@ -1,5 +1,6 @@
-class UserProxyExerciseExercise < ApplicationRecord
+# frozen_string_literal: true
 
+class UserProxyExerciseExercise < ApplicationRecord
   belongs_to :user, polymorphic: true
   belongs_to :exercise
   belongs_to :proxy_exercise
@@ -9,6 +10,5 @@ class UserProxyExerciseExercise < ApplicationRecord
   validates :exercise_id, presence: true
   validates :proxy_exercise_id, presence: true
 
-  validates :user_id, uniqueness: { scope: [:proxy_exercise_id, :user_type] }
-
-end
\ No newline at end of file
+  validates :user_id, uniqueness: {scope: %i[proxy_exercise_id user_type]}
+end
diff --git a/app/policies/admin/dashboard_policy.rb b/app/policies/admin/dashboard_policy.rb
index 673481bd..d8c6ef49 100644
--- a/app/policies/admin/dashboard_policy.rb
+++ b/app/policies/admin/dashboard_policy.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Admin
   class DashboardPolicy < AdminOnlyPolicy
     def dump_docker?
diff --git a/app/policies/admin_only_policy.rb b/app/policies/admin_only_policy.rb
index 1d646594..a577bf64 100644
--- a/app/policies/admin_only_policy.rb
+++ b/app/policies/admin_only_policy.rb
@@ -1,5 +1,7 @@
+# frozen_string_literal: true
+
 class AdminOnlyPolicy < ApplicationPolicy
-  [:create?, :destroy?, :edit?, :index?, :new?, :show?, :update?].each do |action|
+  %i[create? destroy? edit? index? new? show? update?].each do |action|
     define_method(action) { admin? }
   end
 end
diff --git a/app/policies/admin_or_author_policy.rb b/app/policies/admin_or_author_policy.rb
index bf640bad..d510bdd9 100644
--- a/app/policies/admin_or_author_policy.rb
+++ b/app/policies/admin_or_author_policy.rb
@@ -1,9 +1,11 @@
+# frozen_string_literal: true
+
 class AdminOrAuthorPolicy < ApplicationPolicy
-  [:create?, :index?, :new?].each do |action|
+  %i[create? index? new?].each do |action|
     define_method(action) { admin? || teacher? }
   end
 
-  [:destroy?, :edit?, :show?, :update?].each do |action|
+  %i[destroy? edit? show? update?].each do |action|
     define_method(action) { admin? || author? }
   end
 end
diff --git a/app/policies/application_policy.rb b/app/policies/application_policy.rb
index 1b913945..434b61c7 100644
--- a/app/policies/application_policy.rb
+++ b/app/policies/application_policy.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ApplicationPolicy
   def admin?
     @user.admin?
@@ -43,7 +45,7 @@ class ApplicationPolicy
       return false
     end
 
-    @user.study_groups.any?{|i| study_groups.include?(i) }
+    @user.study_groups.any? {|i| study_groups.include?(i) }
   end
   private :everyone_in_study_group
 
@@ -59,7 +61,7 @@ class ApplicationPolicy
   end
 
   def require_user!
-    fail Pundit::NotAuthorizedError unless @user
+    raise Pundit::NotAuthorizedError unless @user
   end
   private :require_user!
 
@@ -71,7 +73,7 @@ class ApplicationPolicy
     end
 
     def require_user!
-      fail Pundit::NotAuthorizedError unless @user
+      raise Pundit::NotAuthorizedError unless @user
     end
     private :require_user!
   end
diff --git a/app/policies/code_ocean/file_policy.rb b/app/policies/code_ocean/file_policy.rb
index 3d5ab473..c9faf30d 100644
--- a/app/policies/code_ocean/file_policy.rb
+++ b/app/policies/code_ocean/file_policy.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module CodeOcean
   class FilePolicy < AdminOrAuthorPolicy
     def author?
@@ -15,7 +17,7 @@ module CodeOcean
     def create?
       if @record.context.is_a?(Exercise)
         admin? || author?
-      elsif @record.context.is_a?(Submission) and @record.context.exercise.allow_file_creation
+      elsif @record.context.is_a?(Submission) && @record.context.exercise.allow_file_creation
         author?
       else
         no_one
diff --git a/app/policies/codeharbor_link_policy.rb b/app/policies/codeharbor_link_policy.rb
index b0dd9a8a..1785f77d 100644
--- a/app/policies/codeharbor_link_policy.rb
+++ b/app/policies/codeharbor_link_policy.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CodeharborLinkPolicy < ApplicationPolicy
   def index?
     false
diff --git a/app/policies/comment_policy.rb b/app/policies/comment_policy.rb
index 41caae9b..d71d5115 100644
--- a/app/policies/comment_policy.rb
+++ b/app/policies/comment_policy.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CommentPolicy < ApplicationPolicy
   def create?
     everyone
@@ -7,7 +9,7 @@ class CommentPolicy < ApplicationPolicy
     everyone
   end
 
-  [:new?, :destroy?, :update?, :edit?].each do |action|
+  %i[new? destroy? update? edit?].each do |action|
     define_method(action) { admin? || author? }
   end
 
diff --git a/app/policies/consumer_policy.rb b/app/policies/consumer_policy.rb
index 8566473d..adbfcac1 100644
--- a/app/policies/consumer_policy.rb
+++ b/app/policies/consumer_policy.rb
@@ -1,3 +1,4 @@
-class ConsumerPolicy < AdminOnlyPolicy
+# frozen_string_literal: true
 
+class ConsumerPolicy < AdminOnlyPolicy
 end
diff --git a/app/policies/error_template_attribute_policy.rb b/app/policies/error_template_attribute_policy.rb
index eed0896d..b793a68f 100644
--- a/app/policies/error_template_attribute_policy.rb
+++ b/app/policies/error_template_attribute_policy.rb
@@ -1,3 +1,4 @@
-class ErrorTemplateAttributePolicy < AdminOnlyPolicy
+# frozen_string_literal: true
 
+class ErrorTemplateAttributePolicy < AdminOnlyPolicy
 end
diff --git a/app/policies/error_template_policy.rb b/app/policies/error_template_policy.rb
index 908be08e..ad9b17bf 100644
--- a/app/policies/error_template_policy.rb
+++ b/app/policies/error_template_policy.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ErrorTemplatePolicy < AdminOnlyPolicy
   def add_attribute?
     admin?
diff --git a/app/policies/event_policy.rb b/app/policies/event_policy.rb
index a648b901..54ae1241 100644
--- a/app/policies/event_policy.rb
+++ b/app/policies/event_policy.rb
@@ -1,7 +1,7 @@
-class EventPolicy < AdminOnlyPolicy
+# frozen_string_literal: true
 
+class EventPolicy < AdminOnlyPolicy
   def create?
     everyone
   end
-
 end
diff --git a/app/policies/execution_environment_policy.rb b/app/policies/execution_environment_policy.rb
index 19da368e..9ed8522c 100644
--- a/app/policies/execution_environment_policy.rb
+++ b/app/policies/execution_environment_policy.rb
@@ -1,5 +1,7 @@
+# frozen_string_literal: true
+
 class ExecutionEnvironmentPolicy < AdminOnlyPolicy
-  [:execute_command?, :shell?, :statistics?, :show?].each do |action|
+  %i[execute_command? shell? statistics? show?].each do |action|
     define_method(action) { admin? || author? }
   end
 
diff --git a/app/policies/exercise_collection_policy.rb b/app/policies/exercise_collection_policy.rb
index 3d6b725e..c53b7e8e 100644
--- a/app/policies/exercise_collection_policy.rb
+++ b/app/policies/exercise_collection_policy.rb
@@ -1,7 +1,7 @@
-class ExerciseCollectionPolicy < AdminOnlyPolicy
+# frozen_string_literal: true
 
+class ExerciseCollectionPolicy < AdminOnlyPolicy
   def statistics?
     admin?
   end
-
 end
diff --git a/app/policies/external_user_policy.rb b/app/policies/external_user_policy.rb
index c35b1eb5..a2c31283 100644
--- a/app/policies/external_user_policy.rb
+++ b/app/policies/external_user_policy.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ExternalUserPolicy < AdminOnlyPolicy
   def index?
     admin? || teacher?
diff --git a/app/policies/file_template_policy.rb b/app/policies/file_template_policy.rb
index 67aad7c0..8467ca94 100644
--- a/app/policies/file_template_policy.rb
+++ b/app/policies/file_template_policy.rb
@@ -1,7 +1,7 @@
-class FileTemplatePolicy < AdminOnlyPolicy
+# frozen_string_literal: true
 
+class FileTemplatePolicy < AdminOnlyPolicy
   def by_file_type?
     everyone
   end
-
 end
diff --git a/app/policies/file_type_policy.rb b/app/policies/file_type_policy.rb
index 57cd4940..957b9e8c 100644
--- a/app/policies/file_type_policy.rb
+++ b/app/policies/file_type_policy.rb
@@ -1,3 +1,4 @@
-class FileTypePolicy < AdminOnlyPolicy
+# frozen_string_literal: true
 
+class FileTypePolicy < AdminOnlyPolicy
 end
diff --git a/app/policies/internal_user_policy.rb b/app/policies/internal_user_policy.rb
index 639a653f..e5bdc6c7 100644
--- a/app/policies/internal_user_policy.rb
+++ b/app/policies/internal_user_policy.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class InternalUserPolicy < AdminOnlyPolicy
   def destroy?
     super && !@record.admin?
diff --git a/app/policies/proxy_exercise_policy.rb b/app/policies/proxy_exercise_policy.rb
index bc26df1b..92d6d58f 100644
--- a/app/policies/proxy_exercise_policy.rb
+++ b/app/policies/proxy_exercise_policy.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ProxyExercisePolicy < AdminOrAuthorPolicy
   def batch_update?
     admin?
@@ -7,8 +9,8 @@ class ProxyExercisePolicy < AdminOrAuthorPolicy
     admin? || teacher_in_study_group? || teacher? && @record.public? || author?
   end
 
-  [:clone?, :destroy?, :edit?, :update?].each do |action|
-    define_method(action) { admin? || author?}
+  %i[clone? destroy? edit? update?].each do |action|
+    define_method(action) { admin? || author? }
   end
 
   [:reload?].each do |action|
diff --git a/app/policies/search_policy.rb b/app/policies/search_policy.rb
index 7f861c30..bbf11b53 100644
--- a/app/policies/search_policy.rb
+++ b/app/policies/search_policy.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class SearchPolicy < AdminOrAuthorPolicy
   def batch_update?
     admin?
@@ -7,8 +9,8 @@ class SearchPolicy < AdminOrAuthorPolicy
     admin? || teacher?
   end
 
-  [:clone?, :destroy?, :edit?, :update?].each do |action|
-    define_method(action) { admin? || author?}
+  %i[clone? destroy? edit? update?].each do |action|
+    define_method(action) { admin? || author? }
   end
 
   [:reload?].each do |action|
diff --git a/app/policies/statistics_policy.rb b/app/policies/statistics_policy.rb
index e04a5f66..f6d1be98 100644
--- a/app/policies/statistics_policy.rb
+++ b/app/policies/statistics_policy.rb
@@ -1,7 +1,7 @@
-class StatisticsPolicy < AdminOnlyPolicy
+# frozen_string_literal: true
 
-  [:graphs?, :user_activity?, :user_activity_history?, :rfc_activity?, :rfc_activity_history?].each do |action|
+class StatisticsPolicy < AdminOnlyPolicy
+  %i[graphs? user_activity? user_activity_history? rfc_activity? rfc_activity_history?].each do |action|
     define_method(action) { admin? }
   end
-
 end
diff --git a/app/policies/study_group_policy.rb b/app/policies/study_group_policy.rb
index f19af1f1..325401bf 100644
--- a/app/policies/study_group_policy.rb
+++ b/app/policies/study_group_policy.rb
@@ -1,9 +1,11 @@
+# frozen_string_literal: true
+
 class StudyGroupPolicy < AdminOnlyPolicy
   def index?
     admin? || teacher?
   end
 
-  [:show?, :destroy?, :edit?, :update?, :stream_la?].each do |action|
+  %i[show? destroy? edit? update? stream_la?].each do |action|
     define_method(action) { admin? || @user.teacher? && @record.present? && @user.study_groups.exists?(@record.id) }
   end
 
diff --git a/app/policies/submission_policy.rb b/app/policies/submission_policy.rb
index d6ca7830..63a7b2b7 100644
--- a/app/policies/submission_policy.rb
+++ b/app/policies/submission_policy.rb
@@ -1,10 +1,13 @@
+# frozen_string_literal: true
+
 class SubmissionPolicy < ApplicationPolicy
   def create?
     everyone
   end
 
   # insights? is used in the flowr_controller.rb as we use it to authorize the user for a submission
-  [:download?, :download_file?, :render_file?, :run?, :score?, :show?, :statistics?, :stop?, :test?, :insights?].each do |action|
+  %i[download? download_file? render_file? run? score? show? statistics? stop? test?
+     insights?].each do |action|
     define_method(action) { admin? || author? }
   end
 
@@ -12,7 +15,6 @@ class SubmissionPolicy < ApplicationPolicy
     admin?
   end
 
-
   def show_study_group?
     admin? || teacher_in_study_group?
   end
diff --git a/app/policies/subscription_policy.rb b/app/policies/subscription_policy.rb
index 6c759837..8d71829b 100644
--- a/app/policies/subscription_policy.rb
+++ b/app/policies/subscription_policy.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class SubscriptionPolicy < ApplicationPolicy
   def create?
     everyone
diff --git a/app/policies/tag_policy.rb b/app/policies/tag_policy.rb
index 88bb28c9..114bc6b0 100644
--- a/app/policies/tag_policy.rb
+++ b/app/policies/tag_policy.rb
@@ -1,5 +1,6 @@
-class TagPolicy < AdminOnlyPolicy
+# frozen_string_literal: true
 
+class TagPolicy < AdminOnlyPolicy
   class Scope < Scope
     def resolve
       if @user.admin? || @user.teacher?
@@ -9,5 +10,4 @@ class TagPolicy < AdminOnlyPolicy
       end
     end
   end
-
 end
diff --git a/app/policies/tip_policy.rb b/app/policies/tip_policy.rb
index b9a313ad..0cca305b 100644
--- a/app/policies/tip_policy.rb
+++ b/app/policies/tip_policy.rb
@@ -1,5 +1,6 @@
-class TipPolicy < AdminOnlyPolicy
+# frozen_string_literal: true
 
+class TipPolicy < AdminOnlyPolicy
   class Scope < Scope
     def resolve
       if @user.admin? || @user.teacher?
@@ -9,5 +10,4 @@ class TipPolicy < AdminOnlyPolicy
       end
     end
   end
-
 end
diff --git a/app/policies/user_exercise_feedback_policy.rb b/app/policies/user_exercise_feedback_policy.rb
index a570a28c..81861e92 100644
--- a/app/policies/user_exercise_feedback_policy.rb
+++ b/app/policies/user_exercise_feedback_policy.rb
@@ -1,5 +1,6 @@
-class UserExerciseFeedbackPolicy < AdminOrAuthorPolicy
+# frozen_string_literal: true
 
+class UserExerciseFeedbackPolicy < AdminOrAuthorPolicy
   def create?
     everyone
   end
@@ -7,5 +8,4 @@ class UserExerciseFeedbackPolicy < AdminOrAuthorPolicy
   def new?
     everyone
   end
-
 end
diff --git a/app/services/exercise_service/check_external.rb b/app/services/exercise_service/check_external.rb
index cf4a818e..2efc6f68 100644
--- a/app/services/exercise_service/check_external.rb
+++ b/app/services/exercise_service/check_external.rb
@@ -10,12 +10,13 @@ module ExerciseService
     def execute
       response = connection.post do |req|
         req.headers['Content-Type'] = 'application/json'
-        req.headers['Authorization'] = 'Bearer ' + @codeharbor_link.api_key
+        req.headers['Authorization'] = "Bearer #{@codeharbor_link.api_key}"
         req.body = {uuid: @uuid}.to_json
       end
       response_hash = JSON.parse(response.body, symbolize_names: true).slice(:exercise_found, :update_right)
 
-      {error: false, message: message(response_hash[:exercise_found], response_hash[:update_right])}.merge(response_hash)
+      {error: false,
+message: message(response_hash[:exercise_found], response_hash[:update_right])}.merge(response_hash)
     rescue Faraday::Error, JSON::ParserError
       {error: true, message: I18n.t('exercises.export_codeharbor.error')}
     end
diff --git a/app/services/exercise_service/push_external.rb b/app/services/exercise_service/push_external.rb
index 3410a7ba..09b777c6 100644
--- a/app/services/exercise_service/push_external.rb
+++ b/app/services/exercise_service/push_external.rb
@@ -13,7 +13,7 @@ module ExerciseService
         response = connection.post do |request|
           request.headers['Content-Type'] = 'application/zip'
           request.headers['Content-Length'] = body.length.to_s
-          request.headers['Authorization'] = 'Bearer ' + @codeharbor_link.api_key
+          request.headers['Authorization'] = "Bearer #{@codeharbor_link.api_key}"
           request.body = body
         end
 
diff --git a/app/services/proforma_service/convert_exercise_to_task.rb b/app/services/proforma_service/convert_exercise_to_task.rb
index 4937acd3..ab91b6dc 100644
--- a/app/services/proforma_service/convert_exercise_to_task.rb
+++ b/app/services/proforma_service/convert_exercise_to_task.rb
@@ -26,7 +26,7 @@ module ProformaService
           tests: tests,
           uuid: uuid,
           language: DEFAULT_LANGUAGE,
-          model_solutions: model_solutions
+          model_solutions: model_solutions,
         }.compact
       )
     end
@@ -37,7 +37,7 @@ module ProformaService
     end
 
     def model_solutions
-      @exercise.files.filter { |file| file.role == 'reference_implementation' }.map do |file|
+      @exercise.files.filter {|file| file.role == 'reference_implementation' }.map do |file|
         Proforma::ModelSolution.new(
           id: "ms-#{file.id}",
           files: model_solution_file(file)
@@ -50,18 +50,20 @@ module ProformaService
         task_file(file).tap do |ms_file|
           ms_file.used_by_grader = false
           ms_file.usage_by_lms = 'display'
-        end
+        end,
       ]
     end
 
     def tests
-      @exercise.files.filter { |file| file.role == 'teacher_defined_test' || file.role == 'teacher_defined_linter' }.map do |file|
+      @exercise.files.filter do |file|
+        file.role == 'teacher_defined_test' || file.role == 'teacher_defined_linter'
+      end.map do |file|
         Proforma::Test.new(
           id: file.id,
           title: file.name,
           files: test_file(file),
           meta_data: {
-            'feedback-message' => file.feedback_message
+            'feedback-message' => file.feedback_message,
           }.compact
         )
       end
@@ -72,13 +74,16 @@ module ProformaService
         task_file(file).tap do |t_file|
           t_file.used_by_grader = true
           t_file.internal_description = 'teacher_defined_test'
-        end
+        end,
       ]
     end
 
     def task_files
       @exercise.files
-               .filter { |file| !file.role.in? %w[reference_implementation teacher_defined_test teacher_defined_linter] }.map do |file|
+        .filter do |file|
+        !file.role.in? %w[reference_implementation teacher_defined_test
+                          teacher_defined_linter]
+      end.map do |file|
         task_file(file)
       end
     end
@@ -96,7 +101,12 @@ module ProformaService
     end
 
     def filename(file)
-      file.path.present? && file.path != '.' ? ::File.join(file.path, file.name_with_extension) : file.name_with_extension
+      if file.path.present? && file.path != '.'
+        ::File.join(file.path,
+          file.name_with_extension)
+      else
+        file.name_with_extension
+      end
     end
 
     def add_content_to_task_file(file, task_file)
diff --git a/app/services/proforma_service/convert_task_to_exercise.rb b/app/services/proforma_service/convert_task_to_exercise.rb
index fe35eab2..658b5be0 100644
--- a/app/services/proforma_service/convert_task_to_exercise.rb
+++ b/app/services/proforma_service/convert_task_to_exercise.rb
@@ -39,11 +39,9 @@ module ProformaService
     end
 
     def task_files
-      @task_files ||= Hash[
-        @task.all_files.reject { |file| file.id == 'ms-placeholder-file' }.map do |task_file|
-          [task_file.id, codeocean_file_from_task_file(task_file)]
-        end
-      ]
+      @task_files ||= @task.all_files.reject {|file| file.id == 'ms-placeholder-file' }.map do |task_file|
+        [task_file.id, codeocean_file_from_task_file(task_file)]
+      end.to_h
     end
 
     def codeocean_file_from_task_file(file)
diff --git a/app/services/proforma_service/import.rb b/app/services/proforma_service/import.rb
index 9a2e6317..e4b5fe12 100644
--- a/app/services/proforma_service/import.rb
+++ b/app/services/proforma_service/import.rb
@@ -39,7 +39,7 @@ module ProformaService
 
     def import_multi
       Zip::File.open(@zip.path) do |zip_file|
-        zip_files = zip_file.filter { |entry| entry.name.match?(/\.zip$/) }
+        zip_files = zip_file.filter {|entry| entry.name.match?(/\.zip$/) }
         begin
           zip_files.map! do |entry|
             store_zip_entry_in_tempfile entry
@@ -65,7 +65,7 @@ module ProformaService
         zip_file.map(&:name)
       end
 
-      filenames.select { |f| f[/\.xml$/] }.any?
+      filenames.select {|f| f[/\.xml$/] }.any?
     rescue Zip::Error
       raise Proforma::InvalidZip
     end
diff --git a/app/uploaders/file_uploader.rb b/app/uploaders/file_uploader.rb
index c108ed98..78b4168d 100644
--- a/app/uploaders/file_uploader.rb
+++ b/app/uploaders/file_uploader.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class FileUploader < CarrierWave::Uploader::Base
   storage :file
 
diff --git a/app/views/code_ocean/files/show.json.jbuilder b/app/views/code_ocean/files/show.json.jbuilder
index 09c6c701..94cef071 100644
--- a/app/views/code_ocean/files/show.json.jbuilder
+++ b/app/views/code_ocean/files/show.json.jbuilder
@@ -1 +1,3 @@
+# frozen_string_literal: true
+
 json.extract! @file, :id, :name_with_extension
diff --git a/app/views/comments/index.json.jbuilder b/app/views/comments/index.json.jbuilder
index e42dd5bf..31850473 100644
--- a/app/views/comments/index.json.jbuilder
+++ b/app/views/comments/index.json.jbuilder
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 json.array!(@comments) do |comment|
   json.extract! comment, :id, :user_id, :file_id, :row, :column, :text, :username, :date, :updated, :editable
   json.url comment_url(comment, format: :json)
diff --git a/app/views/comments/show.json.jbuilder b/app/views/comments/show.json.jbuilder
index 621bd9f6..b804cd4f 100644
--- a/app/views/comments/show.json.jbuilder
+++ b/app/views/comments/show.json.jbuilder
@@ -1 +1,3 @@
+# frozen_string_literal: true
+
 json.extract! @comment, :id, :user_id, :file_id, :row, :column, :text, :created_at, :updated_at
diff --git a/app/views/exercises/reload.json.jbuilder b/app/views/exercises/reload.json.jbuilder
index 8e5d4e3c..3f5793b1 100644
--- a/app/views/exercises/reload.json.jbuilder
+++ b/app/views/exercises/reload.json.jbuilder
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 json.set! :files do
   json.array! @exercise.files.visible, :content, :id
 end
diff --git a/app/views/file_types/show.json.jbuilder b/app/views/file_types/show.json.jbuilder
index 0842614e..8eede65f 100644
--- a/app/views/file_types/show.json.jbuilder
+++ b/app/views/file_types/show.json.jbuilder
@@ -1 +1,3 @@
+# frozen_string_literal: true
+
 json.extract! @file_type, :id, :name, :editor_mode, :file_extension, :executable, :renderable, :binary
diff --git a/app/views/proxy_exercises/reload.json.jbuilder b/app/views/proxy_exercises/reload.json.jbuilder
index 8e5d4e3c..3f5793b1 100644
--- a/app/views/proxy_exercises/reload.json.jbuilder
+++ b/app/views/proxy_exercises/reload.json.jbuilder
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 json.set! :files do
   json.array! @exercise.files.visible, :content, :id
 end
diff --git a/app/views/request_for_comments/index.json.jbuilder b/app/views/request_for_comments/index.json.jbuilder
index eaf4293a..756f4b17 100644
--- a/app/views/request_for_comments/index.json.jbuilder
+++ b/app/views/request_for_comments/index.json.jbuilder
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 json.array!(@request_for_comments) do |request_for_comment|
   json.extract! request_for_comment, :id, :user_id, :exercise_id, :file_id, :user_type
   json.url request_for_comment_url(request_for_comment, format: :json)
diff --git a/app/views/request_for_comments/show.json.jbuilder b/app/views/request_for_comments/show.json.jbuilder
index 443ce0fb..61301c53 100644
--- a/app/views/request_for_comments/show.json.jbuilder
+++ b/app/views/request_for_comments/show.json.jbuilder
@@ -1 +1,3 @@
+# frozen_string_literal: true
+
 json.extract! @request_for_comment, :id, :user_id, :exercise_id, :file_id, :created_at, :updated_at, :user_type, :solved
diff --git a/app/views/submissions/show.json.jbuilder b/app/views/submissions/show.json.jbuilder
index 8ad8960a..9c280bee 100644
--- a/app/views/submissions/show.json.jbuilder
+++ b/app/views/submissions/show.json.jbuilder
@@ -1,7 +1,10 @@
+# frozen_string_literal: true
+
 json.extract! @submission, :id, :files
 json.download_url download_submission_path(@submission, format: :json)
 json.score_url score_submission_path(@submission, format: :json)
-json.download_file_url download_file_submission_path(@submission, 'a.', format: :json).gsub(/a\.\.json$/, '{filename}.json')
+json.download_file_url download_file_submission_path(@submission, 'a.', format: :json).gsub(/a\.\.json$/,
+  '{filename}.json')
 json.render_url render_submission_path(@submission, 'a.', format: :json).gsub(/a\.\.json$/, '{filename}.json')
 json.run_url run_submission_path(@submission, 'a.', format: :json).gsub(/a\.\.json$/, '{filename}.json')
 json.test_url test_submission_path(@submission, 'a.', format: :json).gsub(/a\.\.json$/, '{filename}.json')
diff --git a/config.ru b/config.ru
index 4a3c09a6..6dc83218 100644
--- a/config.ru
+++ b/config.ru
@@ -1,6 +1,8 @@
+# frozen_string_literal: true
+
 # This file is used by Rack-based servers to start the application.
 
-require_relative "config/environment"
+require_relative 'config/environment'
 
 run Rails.application
 Rails.application.load_server
diff --git a/config/application.rb b/config/application.rb
index 17d35456..78b2bee6 100644
--- a/config/application.rb
+++ b/config/application.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative 'boot'
 
 require 'rails/all'
@@ -25,7 +27,7 @@ module CodeOcean
     # The default locale is :en and all translations from config/locales/*.rb,yml are auto loaded.
     # config.i18n.load_path += Dir[Rails.root.join('my', 'locales', '*.{rb,yml}').to_s]
     # config.i18n.default_locale = :de
-    config.i18n.available_locales = [:de, :en]
+    config.i18n.available_locales = %i[de en]
 
     extra_paths = %W[
       #{config.root}/lib
@@ -40,7 +42,7 @@ module CodeOcean
 
     config.action_cable.mount_path = '/cable'
 
-    config.telegraf.tags = { application: 'codeocean' }
+    config.telegraf.tags = {application: 'codeocean'}
 
     config.after_initialize do
       # Initialize the counters according to the db
diff --git a/config/boot.rb b/config/boot.rb
index b9e460ce..c04863fa 100644
--- a/config/boot.rb
+++ b/config/boot.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../Gemfile', __dir__)
 
 require 'bundler/setup' # Set up gems listed in the Gemfile.
diff --git a/config/environment.rb b/config/environment.rb
index d4654f20..b8a976dc 100644
--- a/config/environment.rb
+++ b/config/environment.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Load the Rails application.
 require_relative 'application'
 
diff --git a/config/environments/development.rb b/config/environments/development.rb
index b0e05e12..01edd517 100644
--- a/config/environments/development.rb
+++ b/config/environments/development.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require "active_support/core_ext/integer/time"
+require 'active_support/core_ext/integer/time'
 
 Rails.application.configure do
   # Settings specified here will take precedence over those in config/application.rb.
@@ -26,7 +26,7 @@ Rails.application.configure do
 
     config.cache_store = :memory_store
     config.public_file_server.headers = {
-      'Cache-Control' => "public, max-age=#{2.days.to_i}"
+      'Cache-Control' => "public, max-age=#{2.days.to_i}",
     }
   else
     config.action_controller.perform_caching = false
diff --git a/config/environments/production.rb b/config/environments/production.rb
index 398510a0..39abff0a 100644
--- a/config/environments/production.rb
+++ b/config/environments/production.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require "active_support/core_ext/integer/time"
+require 'active_support/core_ext/integer/time'
 
 Rails.application.configure do
   # Settings specified here will take precedence over those in config/application.rb.
diff --git a/config/environments/test.rb b/config/environments/test.rb
index cfc5d053..0b8ee95a 100644
--- a/config/environments/test.rb
+++ b/config/environments/test.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require "active_support/core_ext/integer/time"
+require 'active_support/core_ext/integer/time'
 
 # The test environment is used exclusively to run your application's
 # test suite. You never need to work with it otherwise. Remember that
@@ -22,7 +22,7 @@ Rails.application.configure do
   # Configure public file server for tests with Cache-Control for performance.
   config.public_file_server.enabled = true
   config.public_file_server.headers = {
-    'Cache-Control' => "public, max-age=#{1.hour.to_i}"
+    'Cache-Control' => "public, max-age=#{1.hour.to_i}",
   }
 
   # Show full error reports and disable caching.
diff --git a/config/initializers/application_controller_renderer.rb b/config/initializers/application_controller_renderer.rb
index 89d2efab..f4556db3 100644
--- a/config/initializers/application_controller_renderer.rb
+++ b/config/initializers/application_controller_renderer.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 # Be sure to restart your server when you modify this file.
 
 # ActiveSupport::Reloader.to_prepare do
diff --git a/config/initializers/assets.rb b/config/initializers/assets.rb
index 949bb44e..fa603a4e 100644
--- a/config/initializers/assets.rb
+++ b/config/initializers/assets.rb
@@ -13,7 +13,7 @@ Rails.application.config.assets.paths << Rails.root.join('node_modules')
 # Precompile additional assets.
 # application.js, application.css, and all non-JS/CSS in the app/assets
 # folder are already added.
-Rails.application.config.assets.precompile += %w( markdown-buttons.png )
+Rails.application.config.assets.precompile += %w[markdown-buttons.png]
 
 # Disable concurrent asset compilation to prevent segfault # https://github.com/sass/sassc-ruby/issues/197
 # Reproduce: `rake assets:clobber`, `rake assets:precompile`. If the command succeeds, it worked
diff --git a/config/initializers/backtrace_silencers.rb b/config/initializers/backtrace_silencers.rb
index 33699c30..d43cc1d2 100644
--- a/config/initializers/backtrace_silencers.rb
+++ b/config/initializers/backtrace_silencers.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Be sure to restart your server when you modify this file.
 
 # You can add backtrace silencers for libraries that you're using but don't wish to see in your backtraces.
@@ -5,4 +7,4 @@
 
 # You can also remove all the silencers if you're trying to debug a problem that might stem from framework code
 # by setting BACKTRACE=1 before calling your invocation, like "BACKTRACE=1 ./bin/rails runner 'MyClass.perform'".
-Rails.backtrace_cleaner.remove_silencers! if ENV["BACKTRACE"]
+Rails.backtrace_cleaner.remove_silencers! if ENV['BACKTRACE']
diff --git a/config/initializers/cookies_serializer.rb b/config/initializers/cookies_serializer.rb
index 5a6a32d3..ee8dff9c 100644
--- a/config/initializers/cookies_serializer.rb
+++ b/config/initializers/cookies_serializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Be sure to restart your server when you modify this file.
 
 # Specify a serializer for the signed and encrypted cookie jars.
diff --git a/config/initializers/filter_parameter_logging.rb b/config/initializers/filter_parameter_logging.rb
index 4b34a036..3babc73f 100644
--- a/config/initializers/filter_parameter_logging.rb
+++ b/config/initializers/filter_parameter_logging.rb
@@ -1,6 +1,8 @@
+# frozen_string_literal: true
+
 # Be sure to restart your server when you modify this file.
 
 # Configure sensitive parameters which will be filtered from the log file.
-Rails.application.config.filter_parameters += [
-  :passw, :secret, :token, :_key, :crypt, :salt, :certificate, :otp, :ssn
+Rails.application.config.filter_parameters += %i[
+  passw secret token _key crypt salt certificate otp ssn
 ]
diff --git a/config/initializers/inflections.rb b/config/initializers/inflections.rb
index 638bf0c7..d6c6e2f7 100644
--- a/config/initializers/inflections.rb
+++ b/config/initializers/inflections.rb
@@ -15,4 +15,3 @@
 ActiveSupport::Inflector.inflections(:en) do |inflect|
   inflect.acronym 'IO'
 end
-
diff --git a/config/initializers/mime_types.rb b/config/initializers/mime_types.rb
index dc189968..6e1d16f0 100644
--- a/config/initializers/mime_types.rb
+++ b/config/initializers/mime_types.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 # Be sure to restart your server when you modify this file.
 
 # Add new mime types for use in respond_to blocks:
diff --git a/config/initializers/monkey_patches.rb b/config/initializers/monkey_patches.rb
index a910b23a..5ae5de8a 100644
--- a/config/initializers/monkey_patches.rb
+++ b/config/initializers/monkey_patches.rb
@@ -1,7 +1,9 @@
+# frozen_string_literal: true
+
 unless Array.respond_to?(:average)
   class Array
     def average
-      inject(:+) / length unless blank?
+      inject(:+) / length if present?
     end
   end
 end
@@ -9,7 +11,7 @@ end
 unless Array.respond_to?(:to_h)
   class Array
     def to_h
-      Hash[self]
+      to_h
     end
   end
 end
diff --git a/config/initializers/permissions_policy.rb b/config/initializers/permissions_policy.rb
index 00f64d71..50bcf4ea 100644
--- a/config/initializers/permissions_policy.rb
+++ b/config/initializers/permissions_policy.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 # Define an application-wide HTTP permissions policy. For further
 # information see https://developers.google.com/web/updates/2018/06/feature-policy
 #
diff --git a/config/initializers/prometheus.rb b/config/initializers/prometheus.rb
index 3f736ab6..0a3fb409 100644
--- a/config/initializers/prometheus.rb
+++ b/config/initializers/prometheus.rb
@@ -3,7 +3,7 @@
 require 'code_ocean/config'
 
 return unless CodeOcean::Config.new(:code_ocean).read[:prometheus_exporter][:enabled] && !defined?(::Rails::Console)
-return if %w[db: assets:].any? { |task| Rake.application.top_level_tasks.to_s.include?(task) }
+return if %w[db: assets:].any? {|task| Rake.application.top_level_tasks.to_s.include?(task) }
 
 # Add metric callbacks to all models
 ActiveSupport.on_load :active_record do
diff --git a/config/initializers/rails_admin.rb b/config/initializers/rails_admin.rb
index e87bc853..489fdd79 100644
--- a/config/initializers/rails_admin.rb
+++ b/config/initializers/rails_admin.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 RailsAdmin.config do |config|
-
   ### Popular gems integration
 
   ## == Devise ==
@@ -63,23 +62,23 @@ RailsAdmin.config do |config|
             per_page(value)
           end
 
-          def total_count()
+          def total_count
             count
           end
 
-          def first_page?()
+          def first_page?
             self == first
           end
 
-          def last_page?()
+          def last_page?
             self == last
           end
         end
       end
+
       module CollectionMethods
-        alias_method :num_pages, :total_pages
+        alias num_pages total_pages
       end
     end
   end
 end
-
diff --git a/config/initializers/session_store.rb b/config/initializers/session_store.rb
index aed61f8c..43ed5fc8 100644
--- a/config/initializers/session_store.rb
+++ b/config/initializers/session_store.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Be sure to restart your server when you modify this file.
 
 Rails.application.config.session_store :cookie_store, key: '_code_ocean_session', expire_after: 1.month
diff --git a/config/initializers/sorcery.rb b/config/initializers/sorcery.rb
index 46d97ff6..abc23dfc 100644
--- a/config/initializers/sorcery.rb
+++ b/config/initializers/sorcery.rb
@@ -1,8 +1,10 @@
+# frozen_string_literal: true
+
 # The first thing you need to configure is which modules you need in your app.
 # The default is nothing which will include only core features (password encryption, login/logout).
 # Available submodules are: :user_activation, :http_basic_auth, :remember_me,
 # :reset_password, :session_timeout, :brute_force_protection, :activity_logging, :external
-Rails.application.config.sorcery.submodules = [:brute_force_protection, :remember_me, :reset_password, :user_activation]
+Rails.application.config.sorcery.submodules = %i[brute_force_protection remember_me reset_password user_activation]
 
 # Here you can configure each submodule's features.
 Rails.application.config.sorcery.configure do |config|
@@ -13,73 +15,62 @@ Rails.application.config.sorcery.configure do |config|
   #
   # config.not_authenticated_action =
 
-
   # When a non logged in user tries to enter a page that requires login, save
   # the URL he wanted to reach, and send him there after login, using 'redirect_back_or_to'.
   # Default: `true`
   #
   # config.save_return_to_url =
 
-
   # Set domain option for cookies; Useful for remember_me submodule.
   # Default: `nil`
   #
   # config.cookie_domain =
 
-
   # -- session timeout --
   # How long in seconds to keep the session alive.
   # Default: `3600`
   #
   # config.session_timeout =
 
-
   # Use the last action as the beginning of session timeout.
   # Default: `false`
   #
   # config.session_timeout_from_last_action =
 
-
   # -- http_basic_auth --
   # What realm to display for which controller name. For example {"My App" => "Application"}
   # Default: `{"application" => "Application"}`
   #
   # config.controller_to_realm_map =
 
-
   # -- activity logging --
   # will register the time of last user login, every login.
   # Default: `true`
   #
   # config.register_login_time =
 
-
   # will register the time of last user logout, every logout.
   # Default: `true`
   #
   # config.register_logout_time =
 
-
   # will register the time of last user action, every action.
   # Default: `true`
   #
   # config.register_last_activity_time =
 
-
   # -- external --
   # What providers are supported by this app, i.e. [:twitter, :facebook, :github, :linkedin, :xing, :google, :liveid] .
   # Default: `[]`
   #
   # config.external_providers =
 
-
   # You can change it by your local ca_file. i.e. '/etc/pki/tls/certs/ca-bundle.crt'
   # Path to ca_file. By default use a internal ca-bundle.crt.
   # Default: `'path/to/ca_file'`
   #
   # config.ca_file =
 
-
   # For information about LinkedIn API:
   # - user info fields go to https://developer.linkedin.com/documents/profile-fields
   # - access permissions go to https://developer.linkedin.com/documents/authentication#granting
@@ -139,7 +130,6 @@ Rails.application.config.sorcery.configure do |config|
   # config.liveid.callback_url = "http://mydomain.com:3000/oauth/callback?provider=liveid"
   # config.liveid.user_info_mapping = {:username => "name"}
 
-
   # --- user config ---
   config.user_config do |user|
     # -- core --
@@ -148,74 +138,62 @@ Rails.application.config.sorcery.configure do |config|
     #
     # user.username_attribute_names =
 
-
     # change *virtual* password attribute, the one which is used until an encrypted one is generated.
     # Default: `:password`
     #
     # user.password_attribute_name =
 
-
     # downcase the username before trying to authenticate, default is false
     # Default: `false`
     #
     user.downcase_username_before_authenticating = true
 
-
     # change default email attribute.
     # Default: `:email`
     #
     # user.email_attribute_name =
 
-
     # change default crypted_password attribute.
     # Default: `:crypted_password`
     #
     # user.crypted_password_attribute_name =
 
-
     # what pattern to use to join the password with the salt
     # Default: `""`
     #
     # user.salt_join_token =
 
-
     # change default salt attribute.
     # Default: `:salt`
     #
     # user.salt_attribute_name =
 
-
     # how many times to apply encryption to the password.
     # Default: `nil`
     #
     # user.stretches =
 
-
     # encryption key used to encrypt reversible encryptions such as AES256.
     # WARNING: If used for users' passwords, changing this key will leave passwords undecryptable!
     # Default: `nil`
     #
     # user.encryption_key =
 
-
     # use an external encryption class.
     # Default: `nil`
     #
     # user.custom_encryption_provider =
 
-
     # encryption algorithm name. See 'encryption_algorithm=' for available options.
     # Default: `:bcrypt`
     #
     # user.encryption_algorithm =
 
-
     # make this configuration inheritable for subclasses. Useful for ActiveRecord's STI.
     # Default: `false`
     #
     # user.subclasses_inherit_config =
 
-
     # -- remember_me --
     # allow the remember_me cookie to settable through AJAX
     # Default: `true`
@@ -227,38 +205,32 @@ Rails.application.config.sorcery.configure do |config|
     #
     # user.remember_me_for =
 
-
     # -- user_activation --
     # the attribute name to hold activation state (active/pending).
     # Default: `:activation_state`
     #
     # user.activation_state_attribute_name =
 
-
     # the attribute name to hold activation code (sent by email).
     # Default: `:activation_token`
     #
     # user.activation_token_attribute_name =
 
-
     # the attribute name to hold activation code expiration date.
     # Default: `:activation_token_expires_at`
     #
     # user.activation_token_expires_at_attribute_name =
 
-
     # how many seconds before the activation code expires. nil for never expires.
     # Default: `nil`
     #
     # user.activation_token_expiration_period =
 
-
     # your mailer class. Required.
     # Default: `nil`
     #
     user.user_activation_mailer = UserMailer
 
-
     # when true sorcery will not automatically
     # email activation details and allow you to
     # manually handle how and when email is sent.
@@ -266,56 +238,47 @@ Rails.application.config.sorcery.configure do |config|
     #
     # user.activation_mailer_disabled =
 
-
     # activation needed email method on your mailer class.
     # Default: `:activation_needed_email`
     #
     # user.activation_needed_email_method_name =
 
-
     # activation success email method on your mailer class.
     # Default: `:activation_success_email`
     #
     # user.activation_success_email_method_name =
 
-
     # do you want to prevent or allow users that did not activate by email to login?
     # Default: `true`
     #
     # user.prevent_non_active_users_to_login =
 
-
     # -- reset_password --
     # reset password code attribute name.
     # Default: `:reset_password_token`
     #
     # user.reset_password_token_attribute_name =
 
-
     # expires at attribute name.
     # Default: `:reset_password_token_expires_at`
     #
     # user.reset_password_token_expires_at_attribute_name =
 
-
     # when was email sent, used for hammering protection.
     # Default: `:reset_password_email_sent_at`
     #
     # user.reset_password_email_sent_at_attribute_name =
 
-
     # mailer class. Needed.
     # Default: `nil`
     #
     user.reset_password_mailer = UserMailer
 
-
     # reset password email method on your mailer class.
     # Default: `:reset_password_email`
     #
     # user.reset_password_email_method_name =
 
-
     # when true sorcery will not automatically
     # email password reset details and allow you to
     # manually handle how and when email is sent
@@ -323,38 +286,32 @@ Rails.application.config.sorcery.configure do |config|
     #
     # user.reset_password_mailer_disabled =
 
-
     # how many seconds before the reset request expires. nil for never expires.
     # Default: `nil`
     #
     # user.reset_password_expiration_period =
 
-
     # hammering protection, how long to wait before allowing another email to be sent.
     # Default: `5 * 60`
     #
     user.reset_password_time_between_emails = 1.minute
 
-
     # -- brute_force_protection --
     # Failed logins attribute name.
     # Default: `:failed_logins_count`
     #
     # user.failed_logins_count_attribute_name =
 
-
     # This field indicates whether user is banned and when it will be active again.
     # Default: `:lock_expires_at`
     #
     # user.lock_expires_at_attribute_name =
 
-
     # How many failed logins allowed.
     # Default: `50`
     #
     # user.consecutive_login_retries_amount_limit =
 
-
     # How long the user should be banned. in seconds. 0 for permanent.
     # Default: `60 * 60`
     #
@@ -387,44 +344,37 @@ Rails.application.config.sorcery.configure do |config|
     #
     # user.last_login_at_attribute_name =
 
-
     # Last logout attribute name.
     # Default: `:last_logout_at`
     #
     # user.last_logout_at_attribute_name =
 
-
     # Last activity attribute name.
     # Default: `:last_activity_at`
     #
     # user.last_activity_at_attribute_name =
 
-
     # How long since last activity is he user defined logged out?
     # Default: `10 * 60`
     #
     # user.activity_timeout =
 
-
     # -- external --
     # Class which holds the various external provider data for this user.
     # Default: `nil`
     #
     # user.authentications_class =
 
-
     # User's identifier in authentications class.
     # Default: `:user_id`
     #
     # user.authentications_user_id_attribute_name =
 
-
     # Provider's identifier in authentications class.
     # Default: `:provider`
     #
     # user.provider_attribute_name =
 
-
     # User's external unique identifier in authentications class.
     # Default: `:uid`
     #
diff --git a/config/initializers/will_paginate.rb b/config/initializers/will_paginate.rb
index bfff0a68..d626a823 100644
--- a/config/initializers/will_paginate.rb
+++ b/config/initializers/will_paginate.rb
@@ -1 +1,3 @@
+# frozen_string_literal: true
+
 WillPaginate.per_page = 20
diff --git a/config/initializers/wrap_parameters.rb b/config/initializers/wrap_parameters.rb
index bbfc3961..2f3c0db4 100644
--- a/config/initializers/wrap_parameters.rb
+++ b/config/initializers/wrap_parameters.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Be sure to restart your server when you modify this file.
 
 # This file contains settings for ActionController::ParamsWrapper which
diff --git a/config/puma.rb b/config/puma.rb
index 58d38795..f771f275 100644
--- a/config/puma.rb
+++ b/config/puma.rb
@@ -1,28 +1,30 @@
+# frozen_string_literal: true
+
 # Puma can serve each request in a thread from an internal thread pool.
 # The `threads` method setting takes two numbers: a minimum and maximum.
 # Any libraries that use thread pools should be configured to match
 # the maximum value specified for Puma. Default is set to 5 threads for minimum
 # and maximum; this matches the default thread size of Active Record.
 #
-max_threads_count = ENV.fetch("RAILS_MAX_THREADS") { 5 }
-min_threads_count = ENV.fetch("RAILS_MIN_THREADS") { max_threads_count }
+max_threads_count = ENV.fetch('RAILS_MAX_THREADS', 5)
+min_threads_count = ENV.fetch('RAILS_MIN_THREADS') { max_threads_count }
 threads min_threads_count, max_threads_count
 
 # Specifies the `worker_timeout` threshold that Puma will use to wait before
 # terminating a worker in development environments.
 #
-worker_timeout 3600 if ENV.fetch("RAILS_ENV", "development") == "development"
+worker_timeout 3600 if ENV.fetch('RAILS_ENV', 'development') == 'development'
 
 # Specifies the `port` that Puma will listen on to receive requests; default is 7000.
 #
-port        ENV.fetch("PORT") { 7000 }
+port        ENV.fetch('PORT', 7000)
 
 # Specifies the `environment` that Puma will run in.
 #
-environment ENV.fetch("RAILS_ENV") { "development" }
+environment ENV.fetch('RAILS_ENV', 'development')
 
 # Specifies the `pidfile` that Puma will use.
-pidfile ENV.fetch("PIDFILE") { "tmp/pids/server.pid" }
+pidfile ENV.fetch('PIDFILE', 'tmp/pids/server.pid')
 
 # Specifies the number of `workers` to boot in clustered mode.
 # Workers are forked web server processes. If using threads and workers together
diff --git a/config/schedule.rb b/config/schedule.rb
index f1236a52..597ca71c 100644
--- a/config/schedule.rb
+++ b/config/schedule.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Use this file to easily define all of your cron jobs.
 #
 # It's helpful, but not entirely necessary to understand cron before proceeding.
@@ -19,7 +21,7 @@
 
 # Learn more: http://github.com/javan/whenever
 
-set :output, Whenever.path + '/log/whenever/whenever_$(date +%Y%m%d%H%M%S).log'
+set :output, "#{Whenever.path}/log/whenever/whenever_$(date +%Y%m%d%H%M%S).log"
 set :environment, ENV['RAILS_ENV'] if ENV['RAILS_ENV']
 
 every 1.day, at: '3:00 am' do
diff --git a/config/spring.rb b/config/spring.rb
index db5bf130..93cd0ff8 100644
--- a/config/spring.rb
+++ b/config/spring.rb
@@ -1,6 +1,8 @@
+# frozen_string_literal: true
+
 Spring.watch(
-  ".ruby-version",
-  ".rbenv-vars",
-  "tmp/restart.txt",
-  "tmp/caching-dev.txt"
+  '.ruby-version',
+  '.rbenv-vars',
+  'tmp/restart.txt',
+  'tmp/caching-dev.txt'
 )
diff --git a/db/migrate/20140625134118_create_exercises.rb b/db/migrate/20140625134118_create_exercises.rb
index 1395ecc3..069c70a1 100644
--- a/db/migrate/20140625134118_create_exercises.rb
+++ b/db/migrate/20140625134118_create_exercises.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateExercises < ActiveRecord::Migration[4.2]
   def change
     create_table :exercises do |t|
diff --git a/db/migrate/20140626143132_create_execution_environments.rb b/db/migrate/20140626143132_create_execution_environments.rb
index 40c50d0b..e4392b57 100644
--- a/db/migrate/20140626143132_create_execution_environments.rb
+++ b/db/migrate/20140626143132_create_execution_environments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateExecutionEnvironments < ActiveRecord::Migration[4.2]
   def change
     create_table :execution_environments do |t|
diff --git a/db/migrate/20140626144036_create_submissions.rb b/db/migrate/20140626144036_create_submissions.rb
index 07242ed1..bccf690b 100644
--- a/db/migrate/20140626144036_create_submissions.rb
+++ b/db/migrate/20140626144036_create_submissions.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateSubmissions < ActiveRecord::Migration[4.2]
   def change
     create_table :submissions do |t|
diff --git a/db/migrate/20140630093736_add_reference_implementation_to_exercises.rb b/db/migrate/20140630093736_add_reference_implementation_to_exercises.rb
index d9a854e2..191f345a 100644
--- a/db/migrate/20140630093736_add_reference_implementation_to_exercises.rb
+++ b/db/migrate/20140630093736_add_reference_implementation_to_exercises.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddReferenceImplementationToExercises < ActiveRecord::Migration[4.2]
   def change
     add_column :exercises, :reference_implementation, :text
diff --git a/db/migrate/20140630111215_add_indent_size_to_execution_environments.rb b/db/migrate/20140630111215_add_indent_size_to_execution_environments.rb
index 6f2830a8..0d77ba74 100644
--- a/db/migrate/20140630111215_add_indent_size_to_execution_environments.rb
+++ b/db/migrate/20140630111215_add_indent_size_to_execution_environments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddIndentSizeToExecutionEnvironments < ActiveRecord::Migration[4.2]
   def change
     add_column :execution_environments, :indent_size, :integer
diff --git a/db/migrate/20140701120126_create_consumers.rb b/db/migrate/20140701120126_create_consumers.rb
index 8efbc84e..705c3f63 100644
--- a/db/migrate/20140701120126_create_consumers.rb
+++ b/db/migrate/20140701120126_create_consumers.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateConsumers < ActiveRecord::Migration[4.2]
   def change
     create_table :consumers do |t|
diff --git a/db/migrate/20140701122345_create_users.rb b/db/migrate/20140701122345_create_users.rb
index 215e0ffb..4501ca21 100644
--- a/db/migrate/20140701122345_create_users.rb
+++ b/db/migrate/20140701122345_create_users.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateUsers < ActiveRecord::Migration[4.2]
   def change
     create_table :users do |t|
diff --git a/db/migrate/20140702100130_add_oauth_key_to_consumers.rb b/db/migrate/20140702100130_add_oauth_key_to_consumers.rb
index e52d914c..5aa24620 100644
--- a/db/migrate/20140702100130_add_oauth_key_to_consumers.rb
+++ b/db/migrate/20140702100130_add_oauth_key_to_consumers.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddOauthKeyToConsumers < ActiveRecord::Migration[4.2]
   def change
     add_column :consumers, :oauth_key, :string
diff --git a/db/migrate/20140703070749_add_oauth_secret_to_consumers.rb b/db/migrate/20140703070749_add_oauth_secret_to_consumers.rb
index 61825748..6a0aeb3d 100644
--- a/db/migrate/20140703070749_add_oauth_secret_to_consumers.rb
+++ b/db/migrate/20140703070749_add_oauth_secret_to_consumers.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddOauthSecretToConsumers < ActiveRecord::Migration[4.2]
   def change
     add_column :consumers, :oauth_secret, :string
diff --git a/db/migrate/20140716153147_add_role_to_users.rb b/db/migrate/20140716153147_add_role_to_users.rb
index 35228ab0..7644985c 100644
--- a/db/migrate/20140716153147_add_role_to_users.rb
+++ b/db/migrate/20140716153147_add_role_to_users.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddRoleToUsers < ActiveRecord::Migration[4.2]
   def change
     add_column :users, :role, :string
diff --git a/db/migrate/20140717074902_add_user_id_to_exercises.rb b/db/migrate/20140717074902_add_user_id_to_exercises.rb
index 55c75391..502fbace 100644
--- a/db/migrate/20140717074902_add_user_id_to_exercises.rb
+++ b/db/migrate/20140717074902_add_user_id_to_exercises.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddUserIdToExercises < ActiveRecord::Migration[4.2]
   def change
     add_reference :exercises, :user
diff --git a/db/migrate/20140722125431_add_run_command_to_execution_environments.rb b/db/migrate/20140722125431_add_run_command_to_execution_environments.rb
index de7e0f21..0d29329f 100644
--- a/db/migrate/20140722125431_add_run_command_to_execution_environments.rb
+++ b/db/migrate/20140722125431_add_run_command_to_execution_environments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddRunCommandToExecutionEnvironments < ActiveRecord::Migration[4.2]
   def change
     add_column :execution_environments, :run_command, :string
diff --git a/db/migrate/20140723135530_add_test_command_to_execution_environments.rb b/db/migrate/20140723135530_add_test_command_to_execution_environments.rb
index fefc57eb..0383367d 100644
--- a/db/migrate/20140723135530_add_test_command_to_execution_environments.rb
+++ b/db/migrate/20140723135530_add_test_command_to_execution_environments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddTestCommandToExecutionEnvironments < ActiveRecord::Migration[4.2]
   def change
     add_column :execution_environments, :test_command, :string
diff --git a/db/migrate/20140723135747_add_test_code_to_exercises.rb b/db/migrate/20140723135747_add_test_code_to_exercises.rb
index 8f184f37..105a479e 100644
--- a/db/migrate/20140723135747_add_test_code_to_exercises.rb
+++ b/db/migrate/20140723135747_add_test_code_to_exercises.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddTestCodeToExercises < ActiveRecord::Migration[4.2]
   def change
     add_column :exercises, :test_code, :text
diff --git a/db/migrate/20140724155359_add_cause_to_submissions.rb b/db/migrate/20140724155359_add_cause_to_submissions.rb
index 37b273ca..73e43a74 100644
--- a/db/migrate/20140724155359_add_cause_to_submissions.rb
+++ b/db/migrate/20140724155359_add_cause_to_submissions.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddCauseToSubmissions < ActiveRecord::Migration[4.2]
   def change
     add_column :submissions, :cause, :string
diff --git a/db/migrate/20140730114343_add_template_test_code_to_exercises.rb b/db/migrate/20140730114343_add_template_test_code_to_exercises.rb
index a0575cbf..7bf5be31 100644
--- a/db/migrate/20140730114343_add_template_test_code_to_exercises.rb
+++ b/db/migrate/20140730114343_add_template_test_code_to_exercises.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddTemplateTestCodeToExercises < ActiveRecord::Migration[4.2]
   def change
     add_column :exercises, :template_test_code, :text
diff --git a/db/migrate/20140730115010_add_supports_user_defined_tests_to_exercises.rb b/db/migrate/20140730115010_add_supports_user_defined_tests_to_exercises.rb
index 401899b6..40cc72d6 100644
--- a/db/migrate/20140730115010_add_supports_user_defined_tests_to_exercises.rb
+++ b/db/migrate/20140730115010_add_supports_user_defined_tests_to_exercises.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddSupportsUserDefinedTestsToExercises < ActiveRecord::Migration[4.2]
   def change
     add_column :exercises, :supports_user_defined_tests, :boolean
diff --git a/db/migrate/20140805161431_add_testing_framework_to_execution_environments.rb b/db/migrate/20140805161431_add_testing_framework_to_execution_environments.rb
index 8b5ea99e..ebce5eca 100644
--- a/db/migrate/20140805161431_add_testing_framework_to_execution_environments.rb
+++ b/db/migrate/20140805161431_add_testing_framework_to_execution_environments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddTestingFrameworkToExecutionEnvironments < ActiveRecord::Migration[4.2]
   def change
     add_column :execution_environments, :testing_framework, :string
diff --git a/db/migrate/20140812102114_create_file_types.rb b/db/migrate/20140812102114_create_file_types.rb
index 22fd2e4c..a2e5d9db 100644
--- a/db/migrate/20140812102114_create_file_types.rb
+++ b/db/migrate/20140812102114_create_file_types.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateFileTypes < ActiveRecord::Migration[4.2]
   def change
     create_table :file_types do |t|
diff --git a/db/migrate/20140812144733_create_files.rb b/db/migrate/20140812144733_create_files.rb
index 789981b9..354179bc 100644
--- a/db/migrate/20140812144733_create_files.rb
+++ b/db/migrate/20140812144733_create_files.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateFiles < ActiveRecord::Migration[4.2]
   def change
     create_table :files do |t|
diff --git a/db/migrate/20140812150607_remove_file_type_related_columns_from_execution_environments.rb b/db/migrate/20140812150607_remove_file_type_related_columns_from_execution_environments.rb
index 53d14dfd..b27a9408 100644
--- a/db/migrate/20140812150607_remove_file_type_related_columns_from_execution_environments.rb
+++ b/db/migrate/20140812150607_remove_file_type_related_columns_from_execution_environments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class RemoveFileTypeRelatedColumnsFromExecutionEnvironments < ActiveRecord::Migration[4.2]
   def change
     remove_column :execution_environments, :editor_mode, :string
diff --git a/db/migrate/20140812150925_remove_file_related_columns_from_exercises.rb b/db/migrate/20140812150925_remove_file_related_columns_from_exercises.rb
index 92954d72..38ff45b0 100644
--- a/db/migrate/20140812150925_remove_file_related_columns_from_exercises.rb
+++ b/db/migrate/20140812150925_remove_file_related_columns_from_exercises.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class RemoveFileRelatedColumnsFromExercises < ActiveRecord::Migration[4.2]
   def change
     remove_column :exercises, :reference_implementation, :text
diff --git a/db/migrate/20140813091722_remove_code_from_submissions.rb b/db/migrate/20140813091722_remove_code_from_submissions.rb
index 2f8ded5e..795a3bb5 100644
--- a/db/migrate/20140813091722_remove_code_from_submissions.rb
+++ b/db/migrate/20140813091722_remove_code_from_submissions.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class RemoveCodeFromSubmissions < ActiveRecord::Migration[4.2]
   def change
     remove_column :submissions, :code, :text
diff --git a/db/migrate/20140820170039_add_instructions_to_exercises.rb b/db/migrate/20140820170039_add_instructions_to_exercises.rb
index aeab4a95..2b9c80cb 100644
--- a/db/migrate/20140820170039_add_instructions_to_exercises.rb
+++ b/db/migrate/20140820170039_add_instructions_to_exercises.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddInstructionsToExercises < ActiveRecord::Migration[4.2]
   def change
     add_column :exercises, :instructions, :text
diff --git a/db/migrate/20140821064318_add_published_to_exercises.rb b/db/migrate/20140821064318_add_published_to_exercises.rb
index 999ba1f5..b999159b 100644
--- a/db/migrate/20140821064318_add_published_to_exercises.rb
+++ b/db/migrate/20140821064318_add_published_to_exercises.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddPublishedToExercises < ActiveRecord::Migration[4.2]
   def change
     add_column :exercises, :published, :boolean
diff --git a/db/migrate/20140823172643_add_executable_to_file_types.rb b/db/migrate/20140823172643_add_executable_to_file_types.rb
index af2f975f..d32dd552 100644
--- a/db/migrate/20140823172643_add_executable_to_file_types.rb
+++ b/db/migrate/20140823172643_add_executable_to_file_types.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddExecutableToFileTypes < ActiveRecord::Migration[4.2]
   def change
     add_column :file_types, :executable, :boolean
diff --git a/db/migrate/20140823173923_add_renderable_to_file_types.rb b/db/migrate/20140823173923_add_renderable_to_file_types.rb
index 034a480a..423aa28d 100644
--- a/db/migrate/20140823173923_add_renderable_to_file_types.rb
+++ b/db/migrate/20140823173923_add_renderable_to_file_types.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddRenderableToFileTypes < ActiveRecord::Migration[4.2]
   def change
     add_column :file_types, :renderable, :boolean
diff --git a/db/migrate/20140825121336_create_external_users.rb b/db/migrate/20140825121336_create_external_users.rb
index e7b9d816..43bc37c5 100644
--- a/db/migrate/20140825121336_create_external_users.rb
+++ b/db/migrate/20140825121336_create_external_users.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateExternalUsers < ActiveRecord::Migration[4.2]
   def change
     create_table :external_users do |t|
diff --git a/db/migrate/20140825125801_create_internal_users.rb b/db/migrate/20140825125801_create_internal_users.rb
index 2ff2c342..c0247675 100644
--- a/db/migrate/20140825125801_create_internal_users.rb
+++ b/db/migrate/20140825125801_create_internal_users.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateInternalUsers < ActiveRecord::Migration[4.2]
   def change
     create_table :internal_users do |t|
diff --git a/db/migrate/20140825154202_drop_users.rb b/db/migrate/20140825154202_drop_users.rb
index 201b6433..5e250fbe 100644
--- a/db/migrate/20140825154202_drop_users.rb
+++ b/db/migrate/20140825154202_drop_users.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class DropUsers < ActiveRecord::Migration[4.2]
   def change
     drop_table :users
diff --git a/db/migrate/20140825161350_add_user_type_to_exercises.rb b/db/migrate/20140825161350_add_user_type_to_exercises.rb
index c9c44d47..f8688499 100644
--- a/db/migrate/20140825161350_add_user_type_to_exercises.rb
+++ b/db/migrate/20140825161350_add_user_type_to_exercises.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddUserTypeToExercises < ActiveRecord::Migration[4.2]
   def change
     add_column :exercises, :user_type, :string
diff --git a/db/migrate/20140825161358_add_user_type_to_file_types.rb b/db/migrate/20140825161358_add_user_type_to_file_types.rb
index 09eb709e..de3c95b2 100644
--- a/db/migrate/20140825161358_add_user_type_to_file_types.rb
+++ b/db/migrate/20140825161358_add_user_type_to_file_types.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddUserTypeToFileTypes < ActiveRecord::Migration[4.2]
   def change
     add_column :file_types, :user_type, :string
diff --git a/db/migrate/20140825161406_add_user_type_to_submissions.rb b/db/migrate/20140825161406_add_user_type_to_submissions.rb
index fd72ba6c..c8c90aa7 100644
--- a/db/migrate/20140825161406_add_user_type_to_submissions.rb
+++ b/db/migrate/20140825161406_add_user_type_to_submissions.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddUserTypeToSubmissions < ActiveRecord::Migration[4.2]
   def change
     add_column :submissions, :user_type, :string
diff --git a/db/migrate/20140826073318_sorcery_core.rb b/db/migrate/20140826073318_sorcery_core.rb
index 077e88b8..ce978f4f 100644
--- a/db/migrate/20140826073318_sorcery_core.rb
+++ b/db/migrate/20140826073318_sorcery_core.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class SorceryCore < ActiveRecord::Migration[4.2]
   def change
     InternalUser.delete_all
diff --git a/db/migrate/20140826073319_sorcery_brute_force_protection.rb b/db/migrate/20140826073319_sorcery_brute_force_protection.rb
index abd9d835..3723acbc 100644
--- a/db/migrate/20140826073319_sorcery_brute_force_protection.rb
+++ b/db/migrate/20140826073319_sorcery_brute_force_protection.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class SorceryBruteForceProtection < ActiveRecord::Migration[4.2]
   def change
     add_column :internal_users, :failed_logins_count, :integer, default: 0
diff --git a/db/migrate/20140826073320_sorcery_remember_me.rb b/db/migrate/20140826073320_sorcery_remember_me.rb
index f232eb09..84429385 100644
--- a/db/migrate/20140826073320_sorcery_remember_me.rb
+++ b/db/migrate/20140826073320_sorcery_remember_me.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class SorceryRememberMe < ActiveRecord::Migration[4.2]
   def change
     add_column :internal_users, :remember_me_token, :string, default: nil
diff --git a/db/migrate/20140826073321_sorcery_reset_password.rb b/db/migrate/20140826073321_sorcery_reset_password.rb
index 74ab7c8d..26a4801c 100644
--- a/db/migrate/20140826073321_sorcery_reset_password.rb
+++ b/db/migrate/20140826073321_sorcery_reset_password.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class SorceryResetPassword < ActiveRecord::Migration[4.2]
   def change
     add_column :internal_users, :reset_password_token, :string, default: nil
diff --git a/db/migrate/20140826073322_sorcery_user_activation.rb b/db/migrate/20140826073322_sorcery_user_activation.rb
index 47fc60f1..cb8758b1 100644
--- a/db/migrate/20140826073322_sorcery_user_activation.rb
+++ b/db/migrate/20140826073322_sorcery_user_activation.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class SorceryUserActivation < ActiveRecord::Migration[4.2]
   def change
     add_column :internal_users, :activation_state, :string, default: nil
diff --git a/db/migrate/20140827065359_add_binary_to_file_types.rb b/db/migrate/20140827065359_add_binary_to_file_types.rb
index 0fa3c65d..fe2d4ea8 100644
--- a/db/migrate/20140827065359_add_binary_to_file_types.rb
+++ b/db/migrate/20140827065359_add_binary_to_file_types.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddBinaryToFileTypes < ActiveRecord::Migration[4.2]
   def change
     add_column :file_types, :binary, :boolean
diff --git a/db/migrate/20140827083957_add_native_file_to_files.rb b/db/migrate/20140827083957_add_native_file_to_files.rb
index cafe27f5..3a92195d 100644
--- a/db/migrate/20140827083957_add_native_file_to_files.rb
+++ b/db/migrate/20140827083957_add_native_file_to_files.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddNativeFileToFiles < ActiveRecord::Migration[4.2]
   def change
     add_column :files, :native_file, :string
diff --git a/db/migrate/20140829141913_create_hints.rb b/db/migrate/20140829141913_create_hints.rb
index ca49c91b..3c8a1464 100644
--- a/db/migrate/20140829141913_create_hints.rb
+++ b/db/migrate/20140829141913_create_hints.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateHints < ActiveRecord::Migration[4.2]
   def change
     create_table :hints do |t|
diff --git a/db/migrate/20140903093436_remove_not_null_constraints_from_internal_users.rb b/db/migrate/20140903093436_remove_not_null_constraints_from_internal_users.rb
index d1f11303..b7f51a13 100644
--- a/db/migrate/20140903093436_remove_not_null_constraints_from_internal_users.rb
+++ b/db/migrate/20140903093436_remove_not_null_constraints_from_internal_users.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class RemoveNotNullConstraintsFromInternalUsers < ActiveRecord::Migration[4.2]
   def change
     change_column_null(:internal_users, :crypted_password, true)
diff --git a/db/migrate/20140903165113_create_errors.rb b/db/migrate/20140903165113_create_errors.rb
index 27534d38..8d9b849d 100644
--- a/db/migrate/20140903165113_create_errors.rb
+++ b/db/migrate/20140903165113_create_errors.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateErrors < ActiveRecord::Migration[4.2]
   def change
     create_table :errors do |t|
diff --git a/db/migrate/20140904082810_add_token_to_exercises.rb b/db/migrate/20140904082810_add_token_to_exercises.rb
index 14e7a459..713210a5 100644
--- a/db/migrate/20140904082810_add_token_to_exercises.rb
+++ b/db/migrate/20140904082810_add_token_to_exercises.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddTokenToExercises < ActiveRecord::Migration[4.2]
   def change
     add_column :exercises, :token, :string
diff --git a/db/migrate/20140909115430_add_file_id_to_exercises.rb b/db/migrate/20140909115430_add_file_id_to_exercises.rb
index 09990eac..4ab10268 100644
--- a/db/migrate/20140909115430_add_file_id_to_exercises.rb
+++ b/db/migrate/20140909115430_add_file_id_to_exercises.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddFileIdToExercises < ActiveRecord::Migration[4.2]
   def change
     add_reference :exercises, :file
diff --git a/db/migrate/20140915095420_add_role_to_files.rb b/db/migrate/20140915095420_add_role_to_files.rb
index 47774e4c..2d57c908 100644
--- a/db/migrate/20140915095420_add_role_to_files.rb
+++ b/db/migrate/20140915095420_add_role_to_files.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddRoleToFiles < ActiveRecord::Migration[4.2]
   def change
     add_column :files, :role, :string
diff --git a/db/migrate/20140915122846_remove_file_id_from_exercises.rb b/db/migrate/20140915122846_remove_file_id_from_exercises.rb
index 955f4d13..9b495a3a 100644
--- a/db/migrate/20140915122846_remove_file_id_from_exercises.rb
+++ b/db/migrate/20140915122846_remove_file_id_from_exercises.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class RemoveFileIdFromExercises < ActiveRecord::Migration[4.2]
   def change
     remove_reference :exercises, :file
diff --git a/db/migrate/20140918063522_add_hashed_content_to_files.rb b/db/migrate/20140918063522_add_hashed_content_to_files.rb
index 44c103f0..f7685207 100644
--- a/db/migrate/20140918063522_add_hashed_content_to_files.rb
+++ b/db/migrate/20140918063522_add_hashed_content_to_files.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddHashedContentToFiles < ActiveRecord::Migration[4.2]
   def change
     add_column :files, :hashed_content, :string
diff --git a/db/migrate/20140922161120_add_feedback_message_to_files.rb b/db/migrate/20140922161120_add_feedback_message_to_files.rb
index a5908e00..4d04a887 100644
--- a/db/migrate/20140922161120_add_feedback_message_to_files.rb
+++ b/db/migrate/20140922161120_add_feedback_message_to_files.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddFeedbackMessageToFiles < ActiveRecord::Migration[4.2]
   def change
     add_column :files, :feedback_message, :string
diff --git a/db/migrate/20140922161226_add_weight_to_files.rb b/db/migrate/20140922161226_add_weight_to_files.rb
index c2664529..d1515f4d 100644
--- a/db/migrate/20140922161226_add_weight_to_files.rb
+++ b/db/migrate/20140922161226_add_weight_to_files.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddWeightToFiles < ActiveRecord::Migration[4.2]
   def change
     add_column :files, :weight, :float
diff --git a/db/migrate/20141003072729_add_help_to_execution_environments.rb b/db/migrate/20141003072729_add_help_to_execution_environments.rb
index 057aac53..54a36f05 100644
--- a/db/migrate/20141003072729_add_help_to_execution_environments.rb
+++ b/db/migrate/20141003072729_add_help_to_execution_environments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddHelpToExecutionEnvironments < ActiveRecord::Migration[4.2]
   def change
     add_column :execution_environments, :help, :text
diff --git a/db/migrate/20141004114747_add_exposed_ports_to_execution_environments.rb b/db/migrate/20141004114747_add_exposed_ports_to_execution_environments.rb
index b930022b..5fcd6c1f 100644
--- a/db/migrate/20141004114747_add_exposed_ports_to_execution_environments.rb
+++ b/db/migrate/20141004114747_add_exposed_ports_to_execution_environments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddExposedPortsToExecutionEnvironments < ActiveRecord::Migration[4.2]
   def change
     add_column :execution_environments, :exposed_ports, :string
diff --git a/db/migrate/20141009110434_add_permitted_execution_time_to_execution_environments.rb b/db/migrate/20141009110434_add_permitted_execution_time_to_execution_environments.rb
index c7c73ca3..210d61d6 100644
--- a/db/migrate/20141009110434_add_permitted_execution_time_to_execution_environments.rb
+++ b/db/migrate/20141009110434_add_permitted_execution_time_to_execution_environments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddPermittedExecutionTimeToExecutionEnvironments < ActiveRecord::Migration[4.2]
   def change
     add_column :execution_environments, :permitted_execution_time, :integer
diff --git a/db/migrate/20141011145303_add_user_id_and_user_type_to_execution_environments.rb b/db/migrate/20141011145303_add_user_id_and_user_type_to_execution_environments.rb
index b0ef78fc..b6e77068 100644
--- a/db/migrate/20141011145303_add_user_id_and_user_type_to_execution_environments.rb
+++ b/db/migrate/20141011145303_add_user_id_and_user_type_to_execution_environments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddUserIdAndUserTypeToExecutionEnvironments < ActiveRecord::Migration[4.2]
   def change
     add_reference :execution_environments, :user
diff --git a/db/migrate/20141017110211_rename_published_to_public.rb b/db/migrate/20141017110211_rename_published_to_public.rb
index f651460c..88547f9f 100644
--- a/db/migrate/20141017110211_rename_published_to_public.rb
+++ b/db/migrate/20141017110211_rename_published_to_public.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class RenamePublishedToPublic < ActiveRecord::Migration[4.2]
   def change
     rename_column :exercises, :published, :public
diff --git a/db/migrate/20141031161603_add_path_to_files.rb b/db/migrate/20141031161603_add_path_to_files.rb
index 46b012d4..234e8d0f 100644
--- a/db/migrate/20141031161603_add_path_to_files.rb
+++ b/db/migrate/20141031161603_add_path_to_files.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddPathToFiles < ActiveRecord::Migration[4.2]
   def change
     add_column :files, :path, :string
diff --git a/db/migrate/20141119131607_create_comments.rb b/db/migrate/20141119131607_create_comments.rb
index eb697231..c572e854 100644
--- a/db/migrate/20141119131607_create_comments.rb
+++ b/db/migrate/20141119131607_create_comments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateComments < ActiveRecord::Migration[4.2]
   def change
     create_table :comments do |t|
diff --git a/db/migrate/20150128083123_create_teams.rb b/db/migrate/20150128083123_create_teams.rb
index f2f7c543..f26722ab 100644
--- a/db/migrate/20150128083123_create_teams.rb
+++ b/db/migrate/20150128083123_create_teams.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateTeams < ActiveRecord::Migration[4.2]
   def change
     create_table :teams do |t|
diff --git a/db/migrate/20150128084834_create_internal_users_teams.rb b/db/migrate/20150128084834_create_internal_users_teams.rb
index ece283c2..c45df2d2 100644
--- a/db/migrate/20150128084834_create_internal_users_teams.rb
+++ b/db/migrate/20150128084834_create_internal_users_teams.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateInternalUsersTeams < ActiveRecord::Migration[4.2]
   def change
     create_table :internal_users_teams do |t|
diff --git a/db/migrate/20150128093003_add_team_id_to_exercises.rb b/db/migrate/20150128093003_add_team_id_to_exercises.rb
index 04c58cd0..c88f3f8f 100644
--- a/db/migrate/20150128093003_add_team_id_to_exercises.rb
+++ b/db/migrate/20150128093003_add_team_id_to_exercises.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddTeamIdToExercises < ActiveRecord::Migration[4.2]
   def change
     add_reference :exercises, :team
diff --git a/db/migrate/20150204080832_add_pool_size_to_execution_environments.rb b/db/migrate/20150204080832_add_pool_size_to_execution_environments.rb
index aab35315..afe35010 100644
--- a/db/migrate/20150204080832_add_pool_size_to_execution_environments.rb
+++ b/db/migrate/20150204080832_add_pool_size_to_execution_environments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddPoolSizeToExecutionEnvironments < ActiveRecord::Migration[4.2]
   def change
     add_column :execution_environments, :pool_size, :integer
diff --git a/db/migrate/20150310150712_add_file_type_id_to_execution_environments.rb b/db/migrate/20150310150712_add_file_type_id_to_execution_environments.rb
index 214bcec0..4bb249f1 100644
--- a/db/migrate/20150310150712_add_file_type_id_to_execution_environments.rb
+++ b/db/migrate/20150310150712_add_file_type_id_to_execution_environments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddFileTypeIdToExecutionEnvironments < ActiveRecord::Migration[4.2]
   def change
     add_reference :execution_environments, :file_type
diff --git a/db/migrate/20150317083739_add_memory_limit_to_execution_environments.rb b/db/migrate/20150317083739_add_memory_limit_to_execution_environments.rb
index 899b7d50..c9a019cc 100644
--- a/db/migrate/20150317083739_add_memory_limit_to_execution_environments.rb
+++ b/db/migrate/20150317083739_add_memory_limit_to_execution_environments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddMemoryLimitToExecutionEnvironments < ActiveRecord::Migration[4.2]
   def change
     add_column :execution_environments, :memory_limit, :integer
diff --git a/db/migrate/20150317115338_add_network_enabled_to_execution_environments.rb b/db/migrate/20150317115338_add_network_enabled_to_execution_environments.rb
index c328a298..e5b62d0a 100644
--- a/db/migrate/20150317115338_add_network_enabled_to_execution_environments.rb
+++ b/db/migrate/20150317115338_add_network_enabled_to_execution_environments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddNetworkEnabledToExecutionEnvironments < ActiveRecord::Migration[4.2]
   def change
     add_column :execution_environments, :network_enabled, :boolean
diff --git a/db/migrate/20150327141740_create_request_for_comments.rb b/db/migrate/20150327141740_create_request_for_comments.rb
index a89b947b..38d3c001 100644
--- a/db/migrate/20150327141740_create_request_for_comments.rb
+++ b/db/migrate/20150327141740_create_request_for_comments.rb
@@ -1,9 +1,11 @@
+# frozen_string_literal: true
+
 class CreateRequestForComments < ActiveRecord::Migration[4.2]
   def change
     create_table :request_for_comments do |t|
-      t.integer :requestorid, :null => false
-      t.integer :exerciseid, :null => false
-      t.integer :fileid, :null => false
+      t.integer :requestorid, null: false
+      t.integer :exerciseid, null: false
+      t.integer :fileid, null: false
       t.timestamp :requested_at
 
       t.timestamps
diff --git a/db/migrate/20150408155923_add_submission_to_error.rb b/db/migrate/20150408155923_add_submission_to_error.rb
index e7363e0d..7b51c10f 100644
--- a/db/migrate/20150408155923_add_submission_to_error.rb
+++ b/db/migrate/20150408155923_add_submission_to_error.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddSubmissionToError < ActiveRecord::Migration[4.2]
   def change
     add_reference :errors, :submission, index: true
diff --git a/db/migrate/20150421074734_add_file_index_to_files.rb b/db/migrate/20150421074734_add_file_index_to_files.rb
index c18d09f1..b6286934 100644
--- a/db/migrate/20150421074734_add_file_index_to_files.rb
+++ b/db/migrate/20150421074734_add_file_index_to_files.rb
@@ -1,5 +1,7 @@
+# frozen_string_literal: true
+
 class AddFileIndexToFiles < ActiveRecord::Migration[4.2]
   def change
-    add_index(:files, [:context_id, :context_type])
+    add_index(:files, %i[context_id context_type])
   end
 end
diff --git a/db/migrate/20150818141554_add_user_type_to_request_for_comments.rb b/db/migrate/20150818141554_add_user_type_to_request_for_comments.rb
index 86eff763..ebc2c8b4 100644
--- a/db/migrate/20150818141554_add_user_type_to_request_for_comments.rb
+++ b/db/migrate/20150818141554_add_user_type_to_request_for_comments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddUserTypeToRequestForComments < ActiveRecord::Migration[4.2]
   def change
     add_column :request_for_comments, :user_type, :string
diff --git a/db/migrate/20150818142251_correct_column_names.rb b/db/migrate/20150818142251_correct_column_names.rb
index 0fcb2d70..58a49af8 100644
--- a/db/migrate/20150818142251_correct_column_names.rb
+++ b/db/migrate/20150818142251_correct_column_names.rb
@@ -1,7 +1,9 @@
+# frozen_string_literal: true
+
 class CorrectColumnNames < ActiveRecord::Migration[4.2]
   def change
-	rename_column :request_for_comments, :requestorid, :requestor_user_id
-  	rename_column :request_for_comments, :exerciseid, :exercise_id
-  	rename_column :request_for_comments, :fileid, :file_id
+    rename_column :request_for_comments, :requestorid, :requestor_user_id
+    rename_column :request_for_comments, :exerciseid, :exercise_id
+    rename_column :request_for_comments, :fileid, :file_id
   end
 end
diff --git a/db/migrate/20150903152727_remove_requestor_from_request_for_comments.rb b/db/migrate/20150903152727_remove_requestor_from_request_for_comments.rb
index 134649bf..d371135d 100644
--- a/db/migrate/20150903152727_remove_requestor_from_request_for_comments.rb
+++ b/db/migrate/20150903152727_remove_requestor_from_request_for_comments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class RemoveRequestorFromRequestForComments < ActiveRecord::Migration[4.2]
   def change
     rename_column :request_for_comments, :requestor_user_id, :user_id
diff --git a/db/migrate/20150922125415_add_hide_file_tree_to_exercises.rb b/db/migrate/20150922125415_add_hide_file_tree_to_exercises.rb
index fce56b0a..a32f7a83 100644
--- a/db/migrate/20150922125415_add_hide_file_tree_to_exercises.rb
+++ b/db/migrate/20150922125415_add_hide_file_tree_to_exercises.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddHideFileTreeToExercises < ActiveRecord::Migration[4.2]
   def change
     add_column :exercises, :hide_file_tree, :boolean
diff --git a/db/migrate/20160204094409_create_code_harbor_links.rb b/db/migrate/20160204094409_create_code_harbor_links.rb
index f159362b..4e9bcf3e 100644
--- a/db/migrate/20160204094409_create_code_harbor_links.rb
+++ b/db/migrate/20160204094409_create_code_harbor_links.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateCodeHarborLinks < ActiveRecord::Migration[4.2]
   def change
     create_table :code_harbor_links do |t|
diff --git a/db/migrate/20160204111716_add_user_to_code_harbor_link.rb b/db/migrate/20160204111716_add_user_to_code_harbor_link.rb
index 0bf4b575..3966bda8 100644
--- a/db/migrate/20160204111716_add_user_to_code_harbor_link.rb
+++ b/db/migrate/20160204111716_add_user_to_code_harbor_link.rb
@@ -1,5 +1,7 @@
+# frozen_string_literal: true
+
 class AddUserToCodeHarborLink < ActiveRecord::Migration[4.2]
   def change
-    add_reference :code_harbor_links, :user,  polymorphic: true, index: true
+    add_reference :code_harbor_links, :user, polymorphic: true, index: true
   end
 end
diff --git a/db/migrate/20160302133540_create_testruns.rb b/db/migrate/20160302133540_create_testruns.rb
index fa622cfe..c791de6a 100644
--- a/db/migrate/20160302133540_create_testruns.rb
+++ b/db/migrate/20160302133540_create_testruns.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateTestruns < ActiveRecord::Migration[4.2]
   def change
     create_table :testruns do |t|
diff --git a/db/migrate/20160426114951_add_question_to_request_for_comments.rb b/db/migrate/20160426114951_add_question_to_request_for_comments.rb
index 31c3f60e..2ac75085 100644
--- a/db/migrate/20160426114951_add_question_to_request_for_comments.rb
+++ b/db/migrate/20160426114951_add_question_to_request_for_comments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddQuestionToRequestForComments < ActiveRecord::Migration[4.2]
   def change
     add_column :request_for_comments, :question, :text
diff --git a/db/migrate/20160510145341_add_allow_file_creation_to_exercises.rb b/db/migrate/20160510145341_add_allow_file_creation_to_exercises.rb
index 37df9904..6206c404 100644
--- a/db/migrate/20160510145341_add_allow_file_creation_to_exercises.rb
+++ b/db/migrate/20160510145341_add_allow_file_creation_to_exercises.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddAllowFileCreationToExercises < ActiveRecord::Migration[4.2]
   def change
     add_column :exercises, :allow_file_creation, :boolean
diff --git a/db/migrate/20160512131539_change_comment_text_attribute_to_text_datatype.rb b/db/migrate/20160512131539_change_comment_text_attribute_to_text_datatype.rb
index 148ec9ea..b00ea047 100644
--- a/db/migrate/20160512131539_change_comment_text_attribute_to_text_datatype.rb
+++ b/db/migrate/20160512131539_change_comment_text_attribute_to_text_datatype.rb
@@ -1,7 +1,10 @@
+# frozen_string_literal: true
+
 class ChangeCommentTextAttributeToTextDatatype < ActiveRecord::Migration[4.2]
   def up
     change_column :comments, :text, :text
   end
+
   def down
     # This might cause trouble if you have strings longer
     # than 255 characters.
diff --git a/db/migrate/20160609185708_create_file_templates.rb b/db/migrate/20160609185708_create_file_templates.rb
index aa111443..83f161e0 100644
--- a/db/migrate/20160609185708_create_file_templates.rb
+++ b/db/migrate/20160609185708_create_file_templates.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateFileTemplates < ActiveRecord::Migration[4.2]
   def change
     create_table :file_templates do |t|
diff --git a/db/migrate/20160610111602_add_file_template_to_file.rb b/db/migrate/20160610111602_add_file_template_to_file.rb
index dbcc83e5..7035f4a9 100644
--- a/db/migrate/20160610111602_add_file_template_to_file.rb
+++ b/db/migrate/20160610111602_add_file_template_to_file.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddFileTemplateToFile < ActiveRecord::Migration[4.2]
   def change
     add_reference :files, :file_template
diff --git a/db/migrate/20160624130951_add_solved_to_request_for_comments.rb b/db/migrate/20160624130951_add_solved_to_request_for_comments.rb
index bfa1e2a1..dbd8dea4 100644
--- a/db/migrate/20160624130951_add_solved_to_request_for_comments.rb
+++ b/db/migrate/20160624130951_add_solved_to_request_for_comments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddSolvedToRequestForComments < ActiveRecord::Migration[4.2]
   def change
     add_column :request_for_comments, :solved, :boolean
diff --git a/db/migrate/20160630154310_add_submission_to_request_for_comments.rb b/db/migrate/20160630154310_add_submission_to_request_for_comments.rb
index 4e2e1494..65dac9f1 100644
--- a/db/migrate/20160630154310_add_submission_to_request_for_comments.rb
+++ b/db/migrate/20160630154310_add_submission_to_request_for_comments.rb
@@ -1,33 +1,33 @@
+# frozen_string_literal: true
+
 class AddSubmissionToRequestForComments < ActiveRecord::Migration[4.2]
   def change
     add_reference :request_for_comments, :submission
   end
 end
 
-=begin
-We issued the following on the database to add the submission_ids for existing entries
-
-UPDATE request_for_comments
-SET submission_id = sub.submission_id_external
-FROM
-(SELECT s.id AS submission_id_external,
-                rfc.id AS rfc_id,
-                          s.created_at AS submission_created_at,
-                                          rfc.created_at AS rfc_created_at
-FROM submissions s,
-                 request_for_comments rfc
-WHERE s.user_id = rfc.user_id
-AND s.exercise_id = rfc.exercise_id
-AND rfc.created_at + interval '2 hours' > s.created_at
-AND s.created_at =
-        (SELECT MAX(created_at)
-        FROM submissions
-        WHERE exercise_id = s.exercise_id
-        AND user_id = s.user_id
-        AND rfc.created_at + interval '2 hours' > created_at
-        GROUP BY s.exercise_id,
-                 s.user_id)) as sub
-WHERE id = sub.rfc_id
-AND submission_id IS NULL;
-
-=end
+# We issued the following on the database to add the submission_ids for existing entries
+#
+# UPDATE request_for_comments
+# SET submission_id = sub.submission_id_external
+# FROM
+# (SELECT s.id AS submission_id_external,
+#                 rfc.id AS rfc_id,
+#                           s.created_at AS submission_created_at,
+#                                           rfc.created_at AS rfc_created_at
+# FROM submissions s,
+#                  request_for_comments rfc
+# WHERE s.user_id = rfc.user_id
+# AND s.exercise_id = rfc.exercise_id
+# AND rfc.created_at + interval '2 hours' > s.created_at
+# AND s.created_at =
+#         (SELECT MAX(created_at)
+#         FROM submissions
+#         WHERE exercise_id = s.exercise_id
+#         AND user_id = s.user_id
+#         AND rfc.created_at + interval '2 hours' > created_at
+#         GROUP BY s.exercise_id,
+#                  s.user_id)) as sub
+# WHERE id = sub.rfc_id
+# AND submission_id IS NULL;
+#
diff --git a/db/migrate/20160701092140_remove_requested_at_from_request_for_comments.rb b/db/migrate/20160701092140_remove_requested_at_from_request_for_comments.rb
index 75f2236a..23a33e1e 100644
--- a/db/migrate/20160701092140_remove_requested_at_from_request_for_comments.rb
+++ b/db/migrate/20160701092140_remove_requested_at_from_request_for_comments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class RemoveRequestedAtFromRequestForComments < ActiveRecord::Migration[4.2]
   def change
     remove_column :request_for_comments, :requested_at
diff --git a/db/migrate/20160704143402_remove_teams.rb b/db/migrate/20160704143402_remove_teams.rb
index f093a4f6..f638a41f 100644
--- a/db/migrate/20160704143402_remove_teams.rb
+++ b/db/migrate/20160704143402_remove_teams.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class RemoveTeams < ActiveRecord::Migration[4.2]
   def change
     remove_reference :exercises, :team
diff --git a/db/migrate/20160907123009_add_allow_auto_completion_to_exercises.rb b/db/migrate/20160907123009_add_allow_auto_completion_to_exercises.rb
index 03ce4757..c99632da 100644
--- a/db/migrate/20160907123009_add_allow_auto_completion_to_exercises.rb
+++ b/db/migrate/20160907123009_add_allow_auto_completion_to_exercises.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddAllowAutoCompletionToExercises < ActiveRecord::Migration[4.2]
   def change
     add_column :exercises, :allow_auto_completion, :boolean, default: false
diff --git a/db/migrate/20170112151637_create_lti_parameters.rb b/db/migrate/20170112151637_create_lti_parameters.rb
index b6370387..d3324786 100644
--- a/db/migrate/20170112151637_create_lti_parameters.rb
+++ b/db/migrate/20170112151637_create_lti_parameters.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateLtiParameters < ActiveRecord::Migration[4.2]
   def change
     create_table :lti_parameters do |t|
@@ -8,4 +10,4 @@ class CreateLtiParameters < ActiveRecord::Migration[4.2]
       t.timestamps
     end
   end
-end
\ No newline at end of file
+end
diff --git a/db/migrate/20170202170437_create_remote_evaluation_mappings.rb b/db/migrate/20170202170437_create_remote_evaluation_mappings.rb
index f04cc2ed..12ba6980 100644
--- a/db/migrate/20170202170437_create_remote_evaluation_mappings.rb
+++ b/db/migrate/20170202170437_create_remote_evaluation_mappings.rb
@@ -1,11 +1,13 @@
+# frozen_string_literal: true
+
 class CreateRemoteEvaluationMappings < ActiveRecord::Migration[4.2]
   def change
     create_table :remote_evaluation_mappings do |t|
-      t.integer   "user_id",          null: false
-      t.integer   "exercise_id",      null: false
-      t.string    "validation_token",  null: false
-      t.datetime  "created_at"
-      t.datetime  "updated_at"
+      t.integer   'user_id',          null: false
+      t.integer   'exercise_id',      null: false
+      t.string    'validation_token', null: false
+      t.datetime  'created_at'
+      t.datetime  'updated_at'
     end
   end
-end
\ No newline at end of file
+end
diff --git a/db/migrate/20170205163247_create_exercise_collections.rb b/db/migrate/20170205163247_create_exercise_collections.rb
index 157a96f8..88abf8c3 100644
--- a/db/migrate/20170205163247_create_exercise_collections.rb
+++ b/db/migrate/20170205163247_create_exercise_collections.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateExerciseCollections < ActiveRecord::Migration[4.2]
   def change
     create_table :exercise_collections do |t|
@@ -9,6 +11,5 @@ class CreateExerciseCollections < ActiveRecord::Migration[4.2]
       t.belongs_to :exercise_collection, index: true
       t.belongs_to :exercise, index: true
     end
-
   end
 end
diff --git a/db/migrate/20170205165450_create_proxy_exercises.rb b/db/migrate/20170205165450_create_proxy_exercises.rb
index 7bb9d8cc..52ef1a55 100644
--- a/db/migrate/20170205165450_create_proxy_exercises.rb
+++ b/db/migrate/20170205165450_create_proxy_exercises.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateProxyExercises < ActiveRecord::Migration[4.2]
   def change
     create_table :proxy_exercises do |t|
diff --git a/db/migrate/20170205210357_create_interventions.rb b/db/migrate/20170205210357_create_interventions.rb
index b8eb3132..97f739b4 100644
--- a/db/migrate/20170205210357_create_interventions.rb
+++ b/db/migrate/20170205210357_create_interventions.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateInterventions < ActiveRecord::Migration[4.2]
   def change
     create_table :user_exercise_interventions do |t|
@@ -16,8 +18,5 @@ class CreateInterventions < ActiveRecord::Migration[4.2]
     end
 
     Intervention.createDefaultInterventions
-
   end
-
-
 end
diff --git a/db/migrate/20170206141210_add_tags.rb b/db/migrate/20170206141210_add_tags.rb
index 77d048af..bdb72e48 100644
--- a/db/migrate/20170206141210_add_tags.rb
+++ b/db/migrate/20170206141210_add_tags.rb
@@ -1,5 +1,6 @@
-class AddTags < ActiveRecord::Migration[4.2]
+# frozen_string_literal: true
 
+class AddTags < ActiveRecord::Migration[4.2]
   def change
     add_column :exercises, :expected_worktime_seconds, :integer, default: 60
     add_column :exercises, :expected_difficulty, :integer, default: 1
@@ -15,5 +16,4 @@ class AddTags < ActiveRecord::Migration[4.2]
       t.integer :factor, default: 1
     end
   end
-
 end
diff --git a/db/migrate/20170206152503_add_user_feedback.rb b/db/migrate/20170206152503_add_user_feedback.rb
index c860e630..e17ad2e9 100644
--- a/db/migrate/20170206152503_add_user_feedback.rb
+++ b/db/migrate/20170206152503_add_user_feedback.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddUserFeedback < ActiveRecord::Migration[4.2]
   def change
     create_table :user_exercise_feedbacks do |t|
diff --git a/db/migrate/20170228165741_add_search.rb b/db/migrate/20170228165741_add_search.rb
index c7168cc6..833a4cb4 100644
--- a/db/migrate/20170228165741_add_search.rb
+++ b/db/migrate/20170228165741_add_search.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddSearch < ActiveRecord::Migration[4.2]
   def change
     create_table :searches do |t|
diff --git a/db/migrate/20170321150454_add_reason_to_user_proxy_exercise_exercise.rb b/db/migrate/20170321150454_add_reason_to_user_proxy_exercise_exercise.rb
index f257dcf3..a6a4e858 100644
--- a/db/migrate/20170321150454_add_reason_to_user_proxy_exercise_exercise.rb
+++ b/db/migrate/20170321150454_add_reason_to_user_proxy_exercise_exercise.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddReasonToUserProxyExerciseExercise < ActiveRecord::Migration[4.2]
   def change
     change_table :user_proxy_exercise_exercises do |t|
diff --git a/db/migrate/20170323130756_add_index_to_submissions.rb b/db/migrate/20170323130756_add_index_to_submissions.rb
index 128f43bb..36200f60 100644
--- a/db/migrate/20170323130756_add_index_to_submissions.rb
+++ b/db/migrate/20170323130756_add_index_to_submissions.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddIndexToSubmissions < ActiveRecord::Migration[4.2]
   def change
     add_index :submissions, :exercise_id
diff --git a/db/migrate/20170403162848_set_default_for_request_for_comment_solved.rb b/db/migrate/20170403162848_set_default_for_request_for_comment_solved.rb
index d952e51a..75e88a53 100644
--- a/db/migrate/20170403162848_set_default_for_request_for_comment_solved.rb
+++ b/db/migrate/20170403162848_set_default_for_request_for_comment_solved.rb
@@ -1,6 +1,8 @@
+# frozen_string_literal: true
+
 class SetDefaultForRequestForCommentSolved < ActiveRecord::Migration[4.2]
   def change
     change_column_default :request_for_comments, :solved, false
     RequestForComment.where(solved: nil).update_all(solved: false)
   end
-end
\ No newline at end of file
+end
diff --git a/db/migrate/20170411090543_improve_user_feedback.rb b/db/migrate/20170411090543_improve_user_feedback.rb
index bf89aafc..c9ab707a 100644
--- a/db/migrate/20170411090543_improve_user_feedback.rb
+++ b/db/migrate/20170411090543_improve_user_feedback.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ImproveUserFeedback < ActiveRecord::Migration[4.2]
   def change
     add_column :user_exercise_feedbacks, :user_estimated_worktime, :integer
diff --git a/db/migrate/20170608141612_add_thank_you_note_to_request_for_comments.rb b/db/migrate/20170608141612_add_thank_you_note_to_request_for_comments.rb
index b75f3589..9f239d4e 100644
--- a/db/migrate/20170608141612_add_thank_you_note_to_request_for_comments.rb
+++ b/db/migrate/20170608141612_add_thank_you_note_to_request_for_comments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddThankYouNoteToRequestForComments < ActiveRecord::Migration[4.2]
   def change
     add_column :request_for_comments, :thank_you_note, :text
diff --git a/db/migrate/20170703075832_create_error_templates.rb b/db/migrate/20170703075832_create_error_templates.rb
index 5556f4ea..59134f42 100644
--- a/db/migrate/20170703075832_create_error_templates.rb
+++ b/db/migrate/20170703075832_create_error_templates.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateErrorTemplates < ActiveRecord::Migration[4.2]
   def change
     create_table :error_templates do |t|
diff --git a/db/migrate/20170703075959_create_error_template_attributes.rb b/db/migrate/20170703075959_create_error_template_attributes.rb
index aa733b09..06ca5849 100644
--- a/db/migrate/20170703075959_create_error_template_attributes.rb
+++ b/db/migrate/20170703075959_create_error_template_attributes.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateErrorTemplateAttributes < ActiveRecord::Migration[4.2]
   def change
     create_table :error_template_attributes do |t|
diff --git a/db/migrate/20170703080205_create_structured_errors.rb b/db/migrate/20170703080205_create_structured_errors.rb
index 111923ca..e6430396 100644
--- a/db/migrate/20170703080205_create_structured_errors.rb
+++ b/db/migrate/20170703080205_create_structured_errors.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateStructuredErrors < ActiveRecord::Migration[4.2]
   def change
     create_table :structured_errors do |t|
diff --git a/db/migrate/20170703080355_create_structured_error_attributes.rb b/db/migrate/20170703080355_create_structured_error_attributes.rb
index 81bc1d19..7ad3f469 100644
--- a/db/migrate/20170703080355_create_structured_error_attributes.rb
+++ b/db/migrate/20170703080355_create_structured_error_attributes.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateStructuredErrorAttributes < ActiveRecord::Migration[4.2]
   def change
     create_table :structured_error_attributes do |t|
diff --git a/db/migrate/20170711170456_add_description_and_hint_to_error_template.rb b/db/migrate/20170711170456_add_description_and_hint_to_error_template.rb
index 11d1985f..223948a3 100644
--- a/db/migrate/20170711170456_add_description_and_hint_to_error_template.rb
+++ b/db/migrate/20170711170456_add_description_and_hint_to_error_template.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddDescriptionAndHintToErrorTemplate < ActiveRecord::Migration[4.2]
   def change
     add_column :error_templates, :description, :text
diff --git a/db/migrate/20170711170928_change_error_template_attribute_relationship_to_n_to_m.rb b/db/migrate/20170711170928_change_error_template_attribute_relationship_to_n_to_m.rb
index 32f3a304..0cc7feaf 100644
--- a/db/migrate/20170711170928_change_error_template_attribute_relationship_to_n_to_m.rb
+++ b/db/migrate/20170711170928_change_error_template_attribute_relationship_to_n_to_m.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ChangeErrorTemplateAttributeRelationshipToNToM < ActiveRecord::Migration[4.2]
   def change
     remove_belongs_to :error_template_attributes, :error_template
diff --git a/db/migrate/20170719133351_add_match_to_structured_error_attribute.rb b/db/migrate/20170719133351_add_match_to_structured_error_attribute.rb
index 51d868ab..bfcfb167 100644
--- a/db/migrate/20170719133351_add_match_to_structured_error_attribute.rb
+++ b/db/migrate/20170719133351_add_match_to_structured_error_attribute.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddMatchToStructuredErrorAttribute < ActiveRecord::Migration[4.2]
   def change
     add_column :structured_error_attributes, :match, :boolean
diff --git a/db/migrate/20170830083601_add_cause_to_testruns.rb b/db/migrate/20170830083601_add_cause_to_testruns.rb
index d737c029..2fea8d54 100644
--- a/db/migrate/20170830083601_add_cause_to_testruns.rb
+++ b/db/migrate/20170830083601_add_cause_to_testruns.rb
@@ -1,15 +1,17 @@
+# frozen_string_literal: true
+
 class AddCauseToTestruns < ActiveRecord::Migration[4.2]
   def up
     add_column :testruns, :cause, :string
     Testrun.reset_column_information
-    Testrun.all.each{ |testrun|
-      if(testrun.submission.nil?)
+    Testrun.all.each do |testrun|
+      if testrun.submission.nil?
         say_with_time "#{testrun.id} has no submission" do end
       else
         testrun.cause = testrun.submission.cause
         testrun.save
       end
-    }
+    end
   end
 
   def down
diff --git a/db/migrate/20170906124500_create_subscriptions.rb b/db/migrate/20170906124500_create_subscriptions.rb
index 83adc2d7..6e4464e5 100644
--- a/db/migrate/20170906124500_create_subscriptions.rb
+++ b/db/migrate/20170906124500_create_subscriptions.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateSubscriptions < ActiveRecord::Migration[4.2]
   def change
     create_table :subscriptions do |t|
diff --git a/db/migrate/20170913054203_rename_subscription_type.rb b/db/migrate/20170913054203_rename_subscription_type.rb
index e380bb07..c061da61 100644
--- a/db/migrate/20170913054203_rename_subscription_type.rb
+++ b/db/migrate/20170913054203_rename_subscription_type.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class RenameSubscriptionType < ActiveRecord::Migration[4.2]
   def change
     rename_column :subscriptions, :type, :subscription_type
diff --git a/db/migrate/20170920145852_add_deleted_to_subscription.rb b/db/migrate/20170920145852_add_deleted_to_subscription.rb
index 6c071b3a..0e1fdc36 100644
--- a/db/migrate/20170920145852_add_deleted_to_subscription.rb
+++ b/db/migrate/20170920145852_add_deleted_to_subscription.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddDeletedToSubscription < ActiveRecord::Migration[4.2]
   def change
     add_column :subscriptions, :deleted, :boolean
diff --git a/db/migrate/20171002131135_remove_expected_working_time.rb b/db/migrate/20171002131135_remove_expected_working_time.rb
index b9d6edd3..29f77102 100644
--- a/db/migrate/20171002131135_remove_expected_working_time.rb
+++ b/db/migrate/20171002131135_remove_expected_working_time.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class RemoveExpectedWorkingTime < ActiveRecord::Migration[4.2]
   def change
     remove_column :exercises, :expected_worktime_seconds
diff --git a/db/migrate/20171115121125_add_anomaly_detection_flag_to_exercise_collection.rb b/db/migrate/20171115121125_add_anomaly_detection_flag_to_exercise_collection.rb
index d9816951..93cf328c 100644
--- a/db/migrate/20171115121125_add_anomaly_detection_flag_to_exercise_collection.rb
+++ b/db/migrate/20171115121125_add_anomaly_detection_flag_to_exercise_collection.rb
@@ -1,5 +1,7 @@
+# frozen_string_literal: true
+
 class AddAnomalyDetectionFlagToExerciseCollection < ActiveRecord::Migration[4.2]
   def change
-    add_column :exercise_collections, :use_anomaly_detection, :boolean, :default => false
+    add_column :exercise_collections, :use_anomaly_detection, :boolean, default: false
   end
 end
diff --git a/db/migrate/20171120153705_add_timestamps_to_user_exercise_feedbacks.rb b/db/migrate/20171120153705_add_timestamps_to_user_exercise_feedbacks.rb
index 7f3bb0c7..1541497d 100644
--- a/db/migrate/20171120153705_add_timestamps_to_user_exercise_feedbacks.rb
+++ b/db/migrate/20171120153705_add_timestamps_to_user_exercise_feedbacks.rb
@@ -1,6 +1,8 @@
+# frozen_string_literal: true
+
 class AddTimestampsToUserExerciseFeedbacks < ActiveRecord::Migration[4.2]
   def up
-    add_column :user_exercise_feedbacks, :created_at, :datetime, null: false, default: Time.now
-    add_column :user_exercise_feedbacks, :updated_at, :datetime, null: false, default: Time.now
+    add_column :user_exercise_feedbacks, :created_at, :datetime, null: false, default: Time.zone.now
+    add_column :user_exercise_feedbacks, :updated_at, :datetime, null: false, default: Time.zone.now
   end
 end
diff --git a/db/migrate/20171122124222_add_index_to_exercises.rb b/db/migrate/20171122124222_add_index_to_exercises.rb
index d02e13bd..e1105a3b 100644
--- a/db/migrate/20171122124222_add_index_to_exercises.rb
+++ b/db/migrate/20171122124222_add_index_to_exercises.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddIndexToExercises < ActiveRecord::Migration[4.2]
   def change
     add_index :exercises, :id
diff --git a/db/migrate/20171210172208_add_user_to_exercise_collection.rb b/db/migrate/20171210172208_add_user_to_exercise_collection.rb
index 6b63120a..af360737 100644
--- a/db/migrate/20171210172208_add_user_to_exercise_collection.rb
+++ b/db/migrate/20171210172208_add_user_to_exercise_collection.rb
@@ -1,5 +1,7 @@
+# frozen_string_literal: true
+
 class AddUserToExerciseCollection < ActiveRecord::Migration[4.2]
   def change
-    add_reference :exercise_collections, :user,  polymorphic: true, index: true
+    add_reference :exercise_collections, :user, polymorphic: true, index: true
   end
 end
diff --git a/db/migrate/20180130101645_add_submission_to_structured_errors.rb b/db/migrate/20180130101645_add_submission_to_structured_errors.rb
index 0f6ccec6..7980cc36 100644
--- a/db/migrate/20180130101645_add_submission_to_structured_errors.rb
+++ b/db/migrate/20180130101645_add_submission_to_structured_errors.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddSubmissionToStructuredErrors < ActiveRecord::Migration[4.2]
   def change
     add_reference :structured_errors, :submission, index: true
diff --git a/db/migrate/20180130172021_add_reached_full_score_to_request_for_comment.rb b/db/migrate/20180130172021_add_reached_full_score_to_request_for_comment.rb
index 651ff184..ffb60187 100644
--- a/db/migrate/20180130172021_add_reached_full_score_to_request_for_comment.rb
+++ b/db/migrate/20180130172021_add_reached_full_score_to_request_for_comment.rb
@@ -1,12 +1,14 @@
+# frozen_string_literal: true
+
 class AddReachedFullScoreToRequestForComment < ActiveRecord::Migration[4.2]
   def up
     add_column :request_for_comments, :full_score_reached, :boolean, default: false
-    RequestForComment.find_each { |rfc|
-      if rfc.submission.present? and rfc.submission.exercise.has_user_solved(rfc.user)
+    RequestForComment.find_each do |rfc|
+      if rfc.submission.present? && rfc.submission.exercise.has_user_solved(rfc.user)
         rfc.full_score_reached = true
         rfc.save
       end
-    }
+    end
   end
 
   def down
diff --git a/db/migrate/20180202132034_add_times_featured_to_request_for_comments.rb b/db/migrate/20180202132034_add_times_featured_to_request_for_comments.rb
index 53194328..58484970 100644
--- a/db/migrate/20180202132034_add_times_featured_to_request_for_comments.rb
+++ b/db/migrate/20180202132034_add_times_featured_to_request_for_comments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddTimesFeaturedToRequestForComments < ActiveRecord::Migration[4.2]
   def change
     add_column :request_for_comments, :times_featured, :integer, default: 0
diff --git a/db/migrate/20180222145909_fix_timestamps_on_feedback.rb b/db/migrate/20180222145909_fix_timestamps_on_feedback.rb
index 32909752..af6f0368 100644
--- a/db/migrate/20180222145909_fix_timestamps_on_feedback.rb
+++ b/db/migrate/20180222145909_fix_timestamps_on_feedback.rb
@@ -1,10 +1,10 @@
+# frozen_string_literal: true
+
 class FixTimestampsOnFeedback < ActiveRecord::Migration[4.2]
   def up
     change_column_default(:user_exercise_feedbacks, :created_at, nil)
     change_column_default(:user_exercise_feedbacks, :updated_at, nil)
   end
 
-  def down
-    
-  end
+  def down; end
 end
diff --git a/db/migrate/20180226131340_create_anomaly_notifications.rb b/db/migrate/20180226131340_create_anomaly_notifications.rb
index c7f4e104..1cfe9db4 100644
--- a/db/migrate/20180226131340_create_anomaly_notifications.rb
+++ b/db/migrate/20180226131340_create_anomaly_notifications.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateAnomalyNotifications < ActiveRecord::Migration[4.2]
   def change
     create_table :anomaly_notifications do |t|
diff --git a/db/migrate/20180515110030_remove_file_id_from_structured_errors.rb b/db/migrate/20180515110030_remove_file_id_from_structured_errors.rb
index c0cd23d1..e8b45138 100644
--- a/db/migrate/20180515110030_remove_file_id_from_structured_errors.rb
+++ b/db/migrate/20180515110030_remove_file_id_from_structured_errors.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class RemoveFileIdFromStructuredErrors < ActiveRecord::Migration[4.2]
   def change
     remove_column :structured_errors, :file_id
diff --git a/db/migrate/20180703125302_create_exercise_collection_items.rb b/db/migrate/20180703125302_create_exercise_collection_items.rb
index aa172c62..ea63a8b6 100644
--- a/db/migrate/20180703125302_create_exercise_collection_items.rb
+++ b/db/migrate/20180703125302_create_exercise_collection_items.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateExerciseCollectionItems < ActiveRecord::Migration[4.2]
   def up
     rename_table :exercise_collections_exercises, :exercise_collection_items
diff --git a/db/migrate/20180814145059_create_events.rb b/db/migrate/20180814145059_create_events.rb
index 5d1eb5e1..02c19ec5 100644
--- a/db/migrate/20180814145059_create_events.rb
+++ b/db/migrate/20180814145059_create_events.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateEvents < ActiveRecord::Migration[4.2]
   def change
     create_table :events do |t|
diff --git a/db/migrate/20180814154055_rename_events_type_to_category.rb b/db/migrate/20180814154055_rename_events_type_to_category.rb
index 9bfe9d0b..f2b83d0a 100644
--- a/db/migrate/20180814154055_rename_events_type_to_category.rb
+++ b/db/migrate/20180814154055_rename_events_type_to_category.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class RenameEventsTypeToCategory < ActiveRecord::Migration[4.2]
   def change
     rename_column :events, :type, :category
diff --git a/db/migrate/20180815115351_remove_event_indices.rb b/db/migrate/20180815115351_remove_event_indices.rb
index fdf7959d..c8cff77b 100644
--- a/db/migrate/20180815115351_remove_event_indices.rb
+++ b/db/migrate/20180815115351_remove_event_indices.rb
@@ -1,6 +1,8 @@
+# frozen_string_literal: true
+
 class RemoveEventIndices < ActiveRecord::Migration[4.2]
   def change
-    remove_index :events, [:user_type, :user_id]
+    remove_index :events, %i[user_type user_id]
     remove_index :events, :exercise_id
     remove_index :events, :file_id
   end
diff --git a/db/migrate/20180823135317_add_index_for_testrun_submission_id.rb b/db/migrate/20180823135317_add_index_for_testrun_submission_id.rb
index 8394660c..f40eedda 100644
--- a/db/migrate/20180823135317_add_index_for_testrun_submission_id.rb
+++ b/db/migrate/20180823135317_add_index_for_testrun_submission_id.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddIndexForTestrunSubmissionId < ActiveRecord::Migration[4.2]
   def change
     add_index :testruns, :submission_id
diff --git a/db/migrate/20180904115948_add_index_for_lti_parameters_external_user_id.rb b/db/migrate/20180904115948_add_index_for_lti_parameters_external_user_id.rb
index e18f9c73..522c2e58 100644
--- a/db/migrate/20180904115948_add_index_for_lti_parameters_external_user_id.rb
+++ b/db/migrate/20180904115948_add_index_for_lti_parameters_external_user_id.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddIndexForLtiParametersExternalUserId < ActiveRecord::Migration[4.2]
   def change
     add_index :lti_parameters, :external_users_id
diff --git a/db/migrate/20181116143743_add_role_to_external_users.rb b/db/migrate/20181116143743_add_role_to_external_users.rb
index 5b4d7066..a6589817 100644
--- a/db/migrate/20181116143743_add_role_to_external_users.rb
+++ b/db/migrate/20181116143743_add_role_to_external_users.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddRoleToExternalUsers < ActiveRecord::Migration[5.2]
   def change
     add_column :external_users, :role, :string, default: 'learner', null: false
diff --git a/db/migrate/20181119161514_add_user_to_proxy_exercise.rb b/db/migrate/20181119161514_add_user_to_proxy_exercise.rb
index 1d9f3192..c19ff639 100644
--- a/db/migrate/20181119161514_add_user_to_proxy_exercise.rb
+++ b/db/migrate/20181119161514_add_user_to_proxy_exercise.rb
@@ -1,6 +1,8 @@
+# frozen_string_literal: true
+
 class AddUserToProxyExercise < ActiveRecord::Migration[5.2]
   def change
-    add_reference :proxy_exercises, :user,  polymorphic: true, index: true
+    add_reference :proxy_exercises, :user, polymorphic: true, index: true
     add_column :proxy_exercises, :public, :boolean, null: false, default: false
 
     internal_user = InternalUser.find_by(id: 46) || InternalUser.first
diff --git a/db/migrate/20181122084546_create_study_groups.rb b/db/migrate/20181122084546_create_study_groups.rb
index 63919d75..82895073 100644
--- a/db/migrate/20181122084546_create_study_groups.rb
+++ b/db/migrate/20181122084546_create_study_groups.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateStudyGroups < ActiveRecord::Migration[5.2]
   def change
     create_table :study_groups do |t|
@@ -7,7 +9,6 @@ class CreateStudyGroups < ActiveRecord::Migration[5.2]
       t.timestamps
     end
 
-    add_index :study_groups, [:external_id, :consumer_id], unique: true
+    add_index :study_groups, %i[external_id consumer_id], unique: true
   end
 end
-
diff --git a/db/migrate/20181122090243_create_study_group_memberships.rb b/db/migrate/20181122090243_create_study_group_memberships.rb
index 8cb34dd3..4de5acf2 100644
--- a/db/migrate/20181122090243_create_study_group_memberships.rb
+++ b/db/migrate/20181122090243_create_study_group_memberships.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateStudyGroupMemberships < ActiveRecord::Migration[5.2]
   def change
     create_table :study_group_memberships do |t|
diff --git a/db/migrate/20181122090244_add_study_group_to_submission.rb b/db/migrate/20181122090244_add_study_group_to_submission.rb
index 94cd30d6..ac8b86f4 100644
--- a/db/migrate/20181122090244_add_study_group_to_submission.rb
+++ b/db/migrate/20181122090244_add_study_group_to_submission.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddStudyGroupToSubmission < ActiveRecord::Migration[5.2]
   def change
     add_reference :submissions, :study_group, index: true, null: true, foreign_key: true
diff --git a/db/migrate/20181126163428_add_user_type_to_remote_evaluation_mappings.rb b/db/migrate/20181126163428_add_user_type_to_remote_evaluation_mappings.rb
index 0ad50d0f..6a1ee2ba 100644
--- a/db/migrate/20181126163428_add_user_type_to_remote_evaluation_mappings.rb
+++ b/db/migrate/20181126163428_add_user_type_to_remote_evaluation_mappings.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddUserTypeToRemoteEvaluationMappings < ActiveRecord::Migration[5.2]
   def change
     add_column :remote_evaluation_mappings, :user_type, :string
diff --git a/db/migrate/20181127160857_drop_hints.rb b/db/migrate/20181127160857_drop_hints.rb
index 83f0905e..ebb58797 100644
--- a/db/migrate/20181127160857_drop_hints.rb
+++ b/db/migrate/20181127160857_drop_hints.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class DropHints < ActiveRecord::Migration[5.2]
   def change
     drop_table :hints
diff --git a/db/migrate/20181129093207_drop_errors.rb b/db/migrate/20181129093207_drop_errors.rb
index 2ec4e82c..e959351c 100644
--- a/db/migrate/20181129093207_drop_errors.rb
+++ b/db/migrate/20181129093207_drop_errors.rb
@@ -1,5 +1,6 @@
-class DropErrors < ActiveRecord::Migration[5.2]
+# frozen_string_literal: true
 
+class DropErrors < ActiveRecord::Migration[5.2]
   # define old CodeOcean::Error module so that the migration works
   module CodeOcean
     class Error < ApplicationRecord
@@ -15,21 +16,16 @@ class DropErrors < ActiveRecord::Migration[5.2]
         true
       end
 
-      def to_s
-        id.to_s
-      end
+      delegate :to_s, to: :id
     end
   end
 
-
-
   def change
-
     puts 'Migrating CodeOcean::Errors to StructuredErrors using RegEx. This might take a (long) while but will return.'
     submissions_controller = SubmissionsController.new
 
     # Iterate only over those Errors containing a message and submission_id
-    CodeOcean::Error.where.not(message: [nil, ""]).where.not(submission_id: [nil, ""]).each do |error|
+    CodeOcean::Error.where.not(message: [nil, '']).where.not(submission_id: [nil, '']).each do |error|
       raw_output = error.message
       submission = Submission.find_by(id: error.submission_id)
 
diff --git a/db/migrate/20190213131802_add_indices_for_request_for_comments.rb b/db/migrate/20190213131802_add_indices_for_request_for_comments.rb
index f0c0dbd4..ab9deeca 100644
--- a/db/migrate/20190213131802_add_indices_for_request_for_comments.rb
+++ b/db/migrate/20190213131802_add_indices_for_request_for_comments.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddIndicesForRequestForComments < ActiveRecord::Migration[5.2]
   def change
     add_index :request_for_comments, :submission_id
diff --git a/db/migrate/20190818104802_rename_code_harbor_links_to_codeharbor_links.rb b/db/migrate/20190818104802_rename_code_harbor_links_to_codeharbor_links.rb
index 5c7ba063..f8b879be 100644
--- a/db/migrate/20190818104802_rename_code_harbor_links_to_codeharbor_links.rb
+++ b/db/migrate/20190818104802_rename_code_harbor_links_to_codeharbor_links.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class RenameCodeHarborLinksToCodeharborLinks < ActiveRecord::Migration[5.2]
   def change
     rename_table :code_harbor_links, :codeharbor_links
diff --git a/db/migrate/20190818104954_add_push_url_rename_oauth2token_in_codeharbor_links.rb b/db/migrate/20190818104954_add_push_url_rename_oauth2token_in_codeharbor_links.rb
index 24dd9137..41106225 100644
--- a/db/migrate/20190818104954_add_push_url_rename_oauth2token_in_codeharbor_links.rb
+++ b/db/migrate/20190818104954_add_push_url_rename_oauth2token_in_codeharbor_links.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddPushUrlRenameOauth2tokenInCodeharborLinks < ActiveRecord::Migration[5.2]
   def change
     add_column :codeharbor_links, :push_url, :string
diff --git a/db/migrate/20190830142809_add_uuid_to_exercise.rb b/db/migrate/20190830142809_add_uuid_to_exercise.rb
index 4dfa6e5c..bd65f8b1 100644
--- a/db/migrate/20190830142809_add_uuid_to_exercise.rb
+++ b/db/migrate/20190830142809_add_uuid_to_exercise.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddUuidToExercise < ActiveRecord::Migration[5.2]
   def change
     add_column :exercises, :uuid, :uuid
diff --git a/db/migrate/20191008163045_add_unpublished_to_exercise.rb b/db/migrate/20191008163045_add_unpublished_to_exercise.rb
index 56bc215d..74a09ed0 100644
--- a/db/migrate/20191008163045_add_unpublished_to_exercise.rb
+++ b/db/migrate/20191008163045_add_unpublished_to_exercise.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddUnpublishedToExercise < ActiveRecord::Migration[5.2]
   def change
     add_column :exercises, :unpublished, :boolean, default: false
diff --git a/db/migrate/20200326115249_add_container_execution_time_to_testruns.rb b/db/migrate/20200326115249_add_container_execution_time_to_testruns.rb
index d04b041d..e4ead4f1 100644
--- a/db/migrate/20200326115249_add_container_execution_time_to_testruns.rb
+++ b/db/migrate/20200326115249_add_container_execution_time_to_testruns.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddContainerExecutionTimeToTestruns < ActiveRecord::Migration[5.2]
   def change
     add_column :testruns, :container_execution_time, :interval
diff --git a/db/migrate/20200506093054_add_deadline_to_exercises.rb b/db/migrate/20200506093054_add_deadline_to_exercises.rb
index 39526198..b4627966 100644
--- a/db/migrate/20200506093054_add_deadline_to_exercises.rb
+++ b/db/migrate/20200506093054_add_deadline_to_exercises.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddDeadlineToExercises < ActiveRecord::Migration[5.2]
   def change
     add_column :exercises, :submission_deadline, :datetime, null: true, default: nil
diff --git a/db/migrate/20201019090123_add_normalized_score_and_submission_to_user_exercise_feedback.rb b/db/migrate/20201019090123_add_normalized_score_and_submission_to_user_exercise_feedback.rb
index cfa13bb0..ef06fce1 100644
--- a/db/migrate/20201019090123_add_normalized_score_and_submission_to_user_exercise_feedback.rb
+++ b/db/migrate/20201019090123_add_normalized_score_and_submission_to_user_exercise_feedback.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddNormalizedScoreAndSubmissionToUserExerciseFeedback < ActiveRecord::Migration[5.2]
   def change
     add_column :user_exercise_feedbacks, :normalized_score, :float
@@ -7,9 +9,9 @@ class AddNormalizedScoreAndSubmissionToUserExerciseFeedback < ActiveRecord::Migr
     ActiveRecord::Base.record_timestamps = false
     UserExerciseFeedback.all.find_each do |uef|
       latest_submission = Submission
-                          .where(user_id: uef.user_id, user_type: uef.user_type, exercise_id: uef.exercise_id)
-                          .where('created_at < ?', uef.updated_at)
-                          .order(created_at: :desc).first
+        .where(user_id: uef.user_id, user_type: uef.user_type, exercise_id: uef.exercise_id)
+        .where('created_at < ?', uef.updated_at)
+        .order(created_at: :desc).first
 
       # In the beginning, CodeOcean allowed feedback for exercises while viewing an RfC. As a RfC
       # might be opened by any registered learner, feedback for exercises was created by learners
diff --git a/db/migrate/20201026184633_create_linter_checks.rb b/db/migrate/20201026184633_create_linter_checks.rb
index 2e98473b..131ca360 100644
--- a/db/migrate/20201026184633_create_linter_checks.rb
+++ b/db/migrate/20201026184633_create_linter_checks.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CreateLinterChecks < ActiveRecord::Migration[5.2]
   def change
     create_table :linter_checks do |t|
diff --git a/db/migrate/20201208095929_add_index_to_rfc.rb b/db/migrate/20201208095929_add_index_to_rfc.rb
index 50bd4d40..92fb7feb 100644
--- a/db/migrate/20201208095929_add_index_to_rfc.rb
+++ b/db/migrate/20201208095929_add_index_to_rfc.rb
@@ -1,6 +1,8 @@
+# frozen_string_literal: true
+
 class AddIndexToRfc < ActiveRecord::Migration[5.2]
   def change
     add_index(:request_for_comments, %i[user_id user_type created_at],
-              order: { user_id: :asc, user_type: :asc, created_at: :desc }, name: :index_rfc_on_user_and_created_at)
+      order: {user_id: :asc, user_type: :asc, created_at: :desc}, name: :index_rfc_on_user_and_created_at)
   end
 end
diff --git a/db/migrate/20201208132844_add_index_to_unpublished_exercises.rb b/db/migrate/20201208132844_add_index_to_unpublished_exercises.rb
index 02d9d06e..26bc578c 100644
--- a/db/migrate/20201208132844_add_index_to_unpublished_exercises.rb
+++ b/db/migrate/20201208132844_add_index_to_unpublished_exercises.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddIndexToUnpublishedExercises < ActiveRecord::Migration[5.2]
   def change
     add_index(:exercises, :id, where: 'NOT unpublished', name: :index_unpublished_exercises)
diff --git a/db/migrate/20201210113500_add_index_to_exercise_title.rb b/db/migrate/20201210113500_add_index_to_exercise_title.rb
index 899ce712..f38be1ea 100644
--- a/db/migrate/20201210113500_add_index_to_exercise_title.rb
+++ b/db/migrate/20201210113500_add_index_to_exercise_title.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class AddIndexToExerciseTitle < ActiveRecord::Migration[5.2]
   def change
     enable_extension 'pg_trgm'
diff --git a/db/migrate/20210512133611_add_service_name_to_active_storage_blobs.active_storage.rb b/db/migrate/20210512133611_add_service_name_to_active_storage_blobs.active_storage.rb
index 18ed13a5..cdfc14f9 100644
--- a/db/migrate/20210512133611_add_service_name_to_active_storage_blobs.active_storage.rb
+++ b/db/migrate/20210512133611_add_service_name_to_active_storage_blobs.active_storage.rb
@@ -1,16 +1,16 @@
+# frozen_string_literal: true
+
 # This migration comes from active_storage (originally 20190112182829)
 class AddServiceNameToActiveStorageBlobs < ActiveRecord::Migration[6.0]
   def up
-    if table_exists?(:active_storage_blobs)
-      unless column_exists?(:active_storage_blobs, :service_name)
-        add_column :active_storage_blobs, :service_name, :string
+    if table_exists?(:active_storage_blobs) && !column_exists?(:active_storage_blobs, :service_name)
+      add_column :active_storage_blobs, :service_name, :string
 
-        if configured_service = ActiveStorage::Blob.service.name
-          ActiveStorage::Blob.unscoped.update_all(service_name: configured_service)
-        end
-
-        change_column :active_storage_blobs, :service_name, :string, null: false
+      if configured_service = ActiveStorage::Blob.service.name
+        ActiveStorage::Blob.unscoped.update_all(service_name: configured_service)
       end
+
+      change_column :active_storage_blobs, :service_name, :string, null: false
     end
   end
 
diff --git a/db/migrate/20210512133612_create_active_storage_variant_records.active_storage.rb b/db/migrate/20210512133612_create_active_storage_variant_records.active_storage.rb
index f131b807..591dbca9 100644
--- a/db/migrate/20210512133612_create_active_storage_variant_records.active_storage.rb
+++ b/db/migrate/20210512133612_create_active_storage_variant_records.active_storage.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # This migration comes from active_storage (originally 20191206030411)
 class CreateActiveStorageVariantRecords < ActiveRecord::Migration[6.0]
   def change
@@ -6,7 +8,7 @@ class CreateActiveStorageVariantRecords < ActiveRecord::Migration[6.0]
         t.belongs_to :blob, null: false, index: false
         t.string :variation_digest, null: false
 
-        t.index %i[ blob_id variation_digest ], name: "index_active_storage_variant_records_uniqueness", unique: true
+        t.index %i[blob_id variation_digest], name: 'index_active_storage_variant_records_uniqueness', unique: true
         t.foreign_key :active_storage_blobs, column: :blob_id
       end
     end
diff --git a/db/seeds.rb b/db/seeds.rb
index 5abc3927..37cfcd55 100644
--- a/db/seeds.rb
+++ b/db/seeds.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 def find_factories_by_class(klass)
   FactoryBot.factories.select do |factory|
     factory.instance_variable_get(:@class_name).to_s == klass.to_s || factory.instance_variable_get(:@name) == klass.model_name.singular.to_sym
@@ -6,7 +8,7 @@ end
 
 module ActiveRecord
   class Base
-    [:build, :create].each do |strategy|
+    %i[build create].each do |strategy|
       define_singleton_method("#{strategy}_factories") do |attributes = {}|
         find_factories_by_class(self).map(&:name).map do |factory_name|
           FactoryBot.send(strategy, factory_name, attributes)
diff --git a/db/seeds/audio_video/index.html_spec.rb b/db/seeds/audio_video/index.html_spec.rb
index b9459550..de9f4a15 100644
--- a/db/seeds/audio_video/index.html_spec.rb
+++ b/db/seeds/audio_video/index.html_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rack/file'
 require 'capybara/rspec'
 
diff --git a/db/seeds/development.rb b/db/seeds/development.rb
index a6d4c17a..87ca3629 100644
--- a/db/seeds/development.rb
+++ b/db/seeds/development.rb
@@ -18,7 +18,7 @@ external_user = FactoryBot.create(:external_user)
 ExecutionEnvironment.create_factories user: admin
 
 # exercises
-@exercises = find_factories_by_class(Exercise).map(&:name).map { |factory_name| [factory_name, FactoryBot.create(factory_name, user: teacher)] }.to_h
+@exercises = find_factories_by_class(Exercise).map(&:name).index_with {|factory_name| FactoryBot.create(factory_name, user: teacher) }
 
 # file types
 FileType.create_factories
diff --git a/db/seeds/fibonacci/exercise.rb b/db/seeds/fibonacci/exercise.rb
index 81652f9d..e0a57e43 100644
--- a/db/seeds/fibonacci/exercise.rb
+++ b/db/seeds/fibonacci/exercise.rb
@@ -1,2 +1,3 @@
-def fibonacci(n)
-end
+# frozen_string_literal: true
+
+def fibonacci(n); end
diff --git a/db/seeds/fibonacci/exercise_spec_1.rb b/db/seeds/fibonacci/exercise_spec_1.rb
index d9937179..428c4537 100644
--- a/db/seeds/fibonacci/exercise_spec_1.rb
+++ b/db/seeds/fibonacci/exercise_spec_1.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require './exercise'
 
 describe '#fibonacci' do
diff --git a/db/seeds/fibonacci/exercise_spec_2.rb b/db/seeds/fibonacci/exercise_spec_2.rb
index 97ba7936..974a18d4 100644
--- a/db/seeds/fibonacci/exercise_spec_2.rb
+++ b/db/seeds/fibonacci/exercise_spec_2.rb
@@ -1,9 +1,11 @@
+# frozen_string_literal: true
+
 require './exercise'
 
 describe '#fibonacci' do
   it 'works recursively' do
     @n = 16
-    expect(self).to receive(:fibonacci).and_call_original.at_least(@n ** 2).times
+    expect(self).to receive(:fibonacci).and_call_original.at_least(@n**2).times
     fibonacci(@n)
   end
 end
diff --git a/db/seeds/fibonacci/exercise_spec_3.rb b/db/seeds/fibonacci/exercise_spec_3.rb
index 68651314..82f6a72b 100644
--- a/db/seeds/fibonacci/exercise_spec_3.rb
+++ b/db/seeds/fibonacci/exercise_spec_3.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require './exercise'
 require './reference'
 
diff --git a/db/seeds/fibonacci/reference.rb b/db/seeds/fibonacci/reference.rb
index 4b202328..6ee48352 100644
--- a/db/seeds/fibonacci/reference.rb
+++ b/db/seeds/fibonacci/reference.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Reference
   def fibonacci(n)
     n < 2 ? n : fibonacci(n - 1) + fibonacci(n - 2)
diff --git a/db/seeds/files/exercise.rb b/db/seeds/files/exercise.rb
index 54198781..92a4ae34 100644
--- a/db/seeds/files/exercise.rb
+++ b/db/seeds/files/exercise.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 SOURCE_FILENAME = 'data.txt'
 TARGET_FILENAME = 'copy.txt'
 
diff --git a/db/seeds/files/exercise_spec.rb b/db/seeds/files/exercise_spec.rb
index 878217ce..11f02fa7 100644
--- a/db/seeds/files/exercise_spec.rb
+++ b/db/seeds/files/exercise_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require './exercise'
 
 describe '#write_to_file' do
diff --git a/db/seeds/hello_world/exercise_spec.rb b/db/seeds/hello_world/exercise_spec.rb
index e7e53ab4..38d08a16 100644
--- a/db/seeds/hello_world/exercise_spec.rb
+++ b/db/seeds/hello_world/exercise_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 describe 'Exercise' do
   it "outputs 'Hello World" do
     expect($stdout).to receive(:puts).with('Hello World')
diff --git a/db/seeds/production.rb b/db/seeds/production.rb
index ad12ee2c..2820de64 100644
--- a/db/seeds/production.rb
+++ b/db/seeds/production.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'highline/import'
 
 # consumers
@@ -7,7 +9,7 @@ FactoryBot.create(:consumer)
 email = ask('Enter admin email: ')
 
 passwords = ['password', 'password confirmation'].map do |attribute|
-  ask("Enter admin #{attribute}: ") { |question| question.echo = false }
+  ask("Enter admin #{attribute}: ") {|question| question.echo = false }
 end
 
 if passwords.uniq.length == 1
diff --git a/db/seeds/sql_select/comparator.rb b/db/seeds/sql_select/comparator.rb
index 715598e5..5b3971c8 100644
--- a/db/seeds/sql_select/comparator.rb
+++ b/db/seeds/sql_select/comparator.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'sqlite3'
 
 REFERENCE_QUERY = File.new('reference.sql', 'r').read
diff --git a/db/seeds/tdd/exercise_spec.rb b/db/seeds/tdd/exercise_spec.rb
index 566cfc94..9ecd2f7a 100644
--- a/db/seeds/tdd/exercise_spec.rb
+++ b/db/seeds/tdd/exercise_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 describe 'Exercise' do
   it 'includes a successful example' do
     expect(true).to be true
diff --git a/db/seeds/web_app/app.rb b/db/seeds/web_app/app.rb
index 76915b6f..5b499849 100644
--- a/db/seeds/web_app/app.rb
+++ b/db/seeds/web_app/app.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'sinatra'
 
 set :bind, '0.0.0.0'
diff --git a/lib/active_model/validations/boolean_presence_validator.rb b/lib/active_model/validations/boolean_presence_validator.rb
index f1fac7dd..80acaafe 100644
--- a/lib/active_model/validations/boolean_presence_validator.rb
+++ b/lib/active_model/validations/boolean_presence_validator.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveModel
   module Validations
     class BooleanPresenceValidator < EachValidator
diff --git a/lib/assessor.rb b/lib/assessor.rb
index 5e018dfa..47612f94 100644
--- a/lib/assessor.rb
+++ b/lib/assessor.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Assessor
   MAXIMUM_SCORE = 1
 
@@ -9,9 +11,9 @@ class Assessor
   end
 
   def calculate_score(test_outcome)
-    score = 0.0;
-    if(test_outcome[:passed].to_f != 0.0 && test_outcome[:count].to_f != 0.0)
-      score = (test_outcome[:passed].to_f / test_outcome[:count].to_f)
+    score = 0.0
+    if test_outcome[:passed].to_f != 0.0 && test_outcome[:count].to_f != 0.0
+      score = (test_outcome[:passed].to_f / test_outcome[:count])
       # prevent negative scores
       score = [0.0, score].max
     end
@@ -23,7 +25,7 @@ class Assessor
     if options[:execution_environment].testing_framework?
       @testing_framework_adapter = Kernel.const_get(options[:execution_environment].testing_framework).new
     else
-      fail(Error, 'No testing framework adapter set!')
+      raise Error.new('No testing framework adapter set!')
     end
   end
 
diff --git a/lib/code_ocean/config.rb b/lib/code_ocean/config.rb
index f73e54b9..f8f186a1 100644
--- a/lib/code_ocean/config.rb
+++ b/lib/code_ocean/config.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module CodeOcean
   class Config
     def initialize(filename)
@@ -7,10 +9,10 @@ module CodeOcean
     def read(options = {})
       path = Rails.root.join('config', "#{@filename}.yml#{options[:erb] ? '.erb' : ''}")
       if ::File.exist?(path)
-        content = options[:erb] ? YAML.load(ERB.new(::File.new(path, 'r').read).result) : YAML.load_file(path)
+        content = options[:erb] ? YAML.safe_load(ERB.new(::File.new(path, 'r').read).result) : YAML.load_file(path)
         content[Rails.env].with_indifferent_access
       else
-        fail(Error, "Configuration file not found: #{path}")
+        raise Error.new("Configuration file not found: #{path}")
       end
     end
 
diff --git a/lib/cpp_catch2_adapter.rb b/lib/cpp_catch2_adapter.rb
index 00a838b4..ea0c21b0 100644
--- a/lib/cpp_catch2_adapter.rb
+++ b/lib/cpp_catch2_adapter.rb
@@ -1,21 +1,23 @@
-class CppCatch2Adapter < TestingFrameworkAdapter
-  ALL_PASSED_REGEXP   		= /in\s+(\d+)\s+test case/ 
-  COUNT_REGEXP      		  = /test cases:\s+(\d+)/
-  FAILURES_REGEXP     		= / \|\s+(\d+)\s+failed/
-  ASSERTION_ERROR_REGEXP 	= /\n(.+)error:(.+);/  
-
-  def self.framework_name
-    'CppCatch2'
-  end
-
-  def parse_output(output)
-    if ALL_PASSED_REGEXP.match(output[:stdout])
-      {count: Regexp.last_match(1).to_i, passed: Regexp.last_match(1).to_i}
-    else
-      count = COUNT_REGEXP.match(output[:stdout]).try(:captures).try(:first).try(:to_i) || 0
-      failed = FAILURES_REGEXP.match(output[:stdout]).try(:captures).try(:first).try(:to_i) || 0
-      error_matches = ASSERTION_ERROR_REGEXP.match(output[:stdout]).try(:captures) || []
-      {count: count, failed: failed, error_messages: error_matches}
-    end
-  end
-end
+# frozen_string_literal: true
+
+class CppCatch2Adapter < TestingFrameworkAdapter
+  ALL_PASSED_REGEXP   		= /in\s+(\d+)\s+test case/.freeze
+  COUNT_REGEXP      		  = /test cases:\s+(\d+)/.freeze
+  FAILURES_REGEXP     		= / \|\s+(\d+)\s+failed/.freeze
+  ASSERTION_ERROR_REGEXP 	= /\n(.+)error:(.+);/.freeze
+
+  def self.framework_name
+    'CppCatch2'
+  end
+
+  def parse_output(output)
+    if ALL_PASSED_REGEXP.match(output[:stdout])
+      {count: Regexp.last_match(1).to_i, passed: Regexp.last_match(1).to_i}
+    else
+      count = COUNT_REGEXP.match(output[:stdout]).try(:captures).try(:first).try(:to_i) || 0
+      failed = FAILURES_REGEXP.match(output[:stdout]).try(:captures).try(:first).try(:to_i) || 0
+      error_matches = ASSERTION_ERROR_REGEXP.match(output[:stdout]).try(:captures) || []
+      {count: count, failed: failed, error_messages: error_matches}
+    end
+  end
+end
diff --git a/lib/docker_client.rb b/lib/docker_client.rb
index c2a0df32..7eb4bc39 100644
--- a/lib/docker_client.rb
+++ b/lib/docker_client.rb
@@ -11,7 +11,7 @@ class DockerClient
   CONTAINER_WORKSPACE_PATH = '/workspace' # '/home/python/workspace' #'/tmp/workspace'
   DEFAULT_MEMORY_LIMIT = 256
   # Ralf: I suggest to replace this with the environment variable. Ask Hauke why this is not the case!
-  LOCAL_WORKSPACE_ROOT = File.expand_path(self.config[:workspace_root])
+  LOCAL_WORKSPACE_ROOT = File.expand_path(config[:workspace_root])
   MINIMUM_MEMORY_LIMIT = 4
   RECYCLE_CONTAINERS = false
   RETRY_COUNT = 2
@@ -19,14 +19,13 @@ class DockerClient
   MAXIMUM_CONTAINER_LIFETIME = 20.minutes
   SELF_DESTROY_GRACE_PERIOD = 2.minutes
 
-  attr_reader :container
-  attr_reader :socket
+  attr_reader :container, :socket
   attr_accessor :tubesock
 
   def self.check_availability!
     Timeout.timeout(config[:connection_timeout]) { Docker.version }
   rescue Excon::Errors::SocketError, Timeout::Error
-    raise(Error, "The Docker host at #{Docker.url} is not reachable!")
+    raise Error.new("The Docker host at #{Docker.url} is not reachable!")
   end
 
   def self.clean_container_workspace(container)
@@ -37,9 +36,9 @@ class DockerClient
     if local_workspace_path && Pathname.new(local_workspace_path).exist?
       Pathname.new(local_workspace_path).children.each do |p|
         p.rmtree
-      rescue Errno::ENOENT, Errno::EACCES => error
-        Sentry.capture_exception(error)
-        Rails.logger.error("clean_container_workspace: Got #{error.class.to_s}: #{error.to_s}")
+      rescue Errno::ENOENT, Errno::EACCES => e
+        Sentry.capture_exception(e)
+        Rails.logger.error("clean_container_workspace: Got #{e.class}: #{e}")
       end
       # FileUtils.rmdir(Pathname.new(local_workspace_path))
     end
@@ -49,7 +48,7 @@ class DockerClient
     {
       class_name: File.basename(filename, File.extname(filename)).camelize,
       filename: filename,
-      module_name: File.basename(filename, File.extname(filename)).underscore
+      module_name: File.basename(filename, File.extname(filename)).underscore,
     }
   end
 
@@ -70,32 +69,32 @@ class DockerClient
       'Binds' => mapped_directories(local_workspace_path),
       'PortBindings' => mapped_ports(execution_environment),
       # Resource limitations.
-      'NanoCPUs' => 4 * 1000000000, # CPU quota in units of 10^-9 CPUs.
+      'NanoCPUs' => 4 * 1_000_000_000, # CPU quota in units of 10^-9 CPUs.
       'PidsLimit' => 100,
       'KernelMemory' => execution_environment.memory_limit.megabytes, # if below Memory, the Docker host (!) might experience an OOM
       'Memory' => execution_environment.memory_limit.megabytes,
       'MemorySwap' => execution_environment.memory_limit.megabytes, # same value as Memory to disable Swap
-      'OomScoreAdj' => 500
+      'OomScoreAdj' => 500,
     }
   end
 
   def create_socket(container, stderr = false)
     # TODO: factor out query params
     # todo separate stderr
-    query_params = 'logs=0&stream=1&' + (stderr ? 'stderr=1' : 'stdout=1&stdin=1')
+    query_params = "logs=0&stream=1&#{stderr ? 'stderr=1' : 'stdout=1&stdin=1'}"
 
     # Headers are required by Docker
     headers = {'Origin' => 'http://localhost'}
 
-    socket_url = DockerClient.config['ws_host'] + '/v1.27/containers/' + @container.id + '/attach/ws?' + query_params
+    socket_url = "#{DockerClient.config['ws_host']}/v1.27/containers/#{@container.id}/attach/ws?#{query_params}"
     # The ping value is measured in seconds and specifies how often a Ping frame should be sent.
     # Internally, Faye::WebSocket uses EventMachine and the ping value is used to wake the EventMachine thread
     socket = Faye::WebSocket::Client.new(socket_url, [], headers: headers, ping: 0.1)
 
-    Rails.logger.debug 'Opening Websocket on URL ' + socket_url
+    Rails.logger.debug "Opening Websocket on URL #{socket_url}"
 
     socket.on :error do |event|
-      Rails.logger.info 'Websocket error: ' + event.message.to_s
+      Rails.logger.info "Websocket error: #{event.message}"
     end
     socket.on :close do |_event|
       Rails.logger.info 'Websocket closed.'
@@ -117,10 +116,10 @@ class DockerClient
     # this is however not guaranteed and caused issues on the server already. Therefore create the necessary folders manually!
     local_workspace_path = generate_local_workspace_path
     FileUtils.mkdir(local_workspace_path)
-    FileUtils.chmod_R(0777, local_workspace_path)
+    FileUtils.chmod_R(0o777, local_workspace_path)
     container = Docker::Container.create(container_creation_options(execution_environment, local_workspace_path))
     container.start
-    container.start_time = Time.now
+    container.start_time = Time.zone.now
     container.status = :created
     container.execution_environment = execution_environment
     container.re_use = true
@@ -130,19 +129,19 @@ class DockerClient
       timeout = Random.rand(MINIMUM_CONTAINER_LIFETIME..MAXIMUM_CONTAINER_LIFETIME) # seconds
       sleep(timeout)
       container.re_use = false
-      if container.status != :executing
-        container.docker_client.kill_container(container, false)
-        Rails.logger.info('Killing container in status ' + container.status.to_s + ' after ' + (Time.now - container.start_time).to_s + ' seconds.')
-      else
+      if container.status == :executing
         Thread.new do
           timeout = SELF_DESTROY_GRACE_PERIOD.to_i
           sleep(timeout)
           container.docker_client.kill_container(container, false)
-          Rails.logger.info('Force killing container in status ' + container.status.to_s + ' after ' + (Time.now - container.start_time).to_s + ' seconds.')
+          Rails.logger.info("Force killing container in status #{container.status} after #{Time.zone.now - container.start_time} seconds.")
         ensure
           # guarantee that the thread is releasing the DB connection after it is done
           ActiveRecord::Base.connection_pool.release_connection
         end
+      else
+        container.docker_client.kill_container(container, false)
+        Rails.logger.info("Killing container in status #{container.status} after #{Time.zone.now - container.start_time} seconds.")
       end
     ensure
       # guarantee that the thread is releasing the DB connection after it is done
@@ -150,8 +149,8 @@ class DockerClient
     end
 
     container
-  rescue Docker::Error::NotFoundError => error
-    Rails.logger.error('create_container: Got Docker::Error::NotFoundError: ' + error.to_s)
+  rescue Docker::Error::NotFoundError => e
+    Rails.logger.error("create_container: Got Docker::Error::NotFoundError: #{e}")
     destroy_container(container)
     # (tries += 1) <= RETRY_COUNT ? retry : raise(error)
   end
@@ -169,7 +168,7 @@ class DockerClient
     end
     FileUtils.chmod_R('+rwX', self.class.local_workspace_path(container))
   rescue Docker::Error::NotFoundError => e
-    Rails.logger.info('create_workspace_files: Rescued from Docker::Error::NotFoundError: ' + e.to_s)
+    Rails.logger.info("create_workspace_files: Rescued from Docker::Error::NotFoundError: #{e}")
   end
 
   private :create_workspace_files
@@ -187,7 +186,7 @@ class DockerClient
     # create a temporary dir, put all files in it, and put it into the container. the dir is automatically removed when leaving the block.
     Dir.mktmpdir do |dir|
       submission.collect_files.each do |file|
-        disk_file = File.new(dir + '/' + (file.path || '') + file.name_with_extension, 'w')
+        disk_file = File.new("#{dir}/#{file.path || ''}#{file.name_with_extension}", 'w')
         disk_file.write(file.content)
         disk_file.close
       end
@@ -198,7 +197,7 @@ class DockerClient
         # container.exec(['bash', '-c', 'chown -R python ' + CONTAINER_WORKSPACE_PATH])
         # container.exec(['bash', '-c', 'chgrp -G python ' + CONTAINER_WORKSPACE_PATH])
       rescue StandardError => e
-        Rails.logger.error('create workspace folder: Rescued from StandardError: ' + e.to_s)
+        Rails.logger.error("create workspace folder: Rescued from StandardError: #{e}")
       end
 
       # sleep 1000
@@ -207,38 +206,39 @@ class DockerClient
         # tar the files in dir and put the tar to CONTAINER_WORKSPACE_PATH in the container
         container.archive_in(dir, CONTAINER_WORKSPACE_PATH, overwrite: false)
       rescue StandardError => e
-        Rails.logger.error('insert tar: Rescued from StandardError: ' + e.to_s)
+        Rails.logger.error("insert tar: Rescued from StandardError: #{e}")
       end
 
       # Rails.logger.info('command: tar -xf ' + CONTAINER_WORKSPACE_PATH  + '/' + dir.split('/tmp/')[1] + ' -C ' + CONTAINER_WORKSPACE_PATH)
 
       begin
         # untar the tar file placed in the CONTAINER_WORKSPACE_PATH
-        container.exec(['bash', '-c', 'tar -xf ' + CONTAINER_WORKSPACE_PATH + '/' + dir.split('/tmp/')[1] + ' -C ' + CONTAINER_WORKSPACE_PATH])
+        container.exec(['bash', '-c',
+                        "tar -xf #{CONTAINER_WORKSPACE_PATH}/#{dir.split('/tmp/')[1]} -C #{CONTAINER_WORKSPACE_PATH}"])
       rescue StandardError => e
-        Rails.logger.error('untar: Rescued from StandardError: ' + e.to_s)
+        Rails.logger.error("untar: Rescued from StandardError: #{e}")
       end
 
       # sleep 1000
     end
   rescue StandardError => e
-    Rails.logger.error('create_workspace_files_transmit: Rescued from StandardError: ' + e.to_s)
+    Rails.logger.error("create_workspace_files_transmit: Rescued from StandardError: #{e}")
   end
 
   def self.destroy_container(container)
     @socket&.close
-    Rails.logger.info('destroying container ' + container.to_s)
+    Rails.logger.info("destroying container #{container}")
 
     # Checks only if container assignment is not nil and not whether the container itself is still present.
     if container && !DockerContainerPool.config[:active]
       container.kill
-      container.port_bindings.values.each { |port| PortPool.release(port) }
+      container.port_bindings.each_value {|port| PortPool.release(port) }
       begin
         clean_container_workspace(container)
         FileUtils.rmtree(local_workspace_path(container))
-      rescue Errno::ENOENT, Errno::EACCES => error
-        Sentry.capture_exception(error)
-        Rails.logger.error("clean_container_workspace: Got #{error.class.to_s}: #{error.to_s}")
+      rescue Errno::ENOENT, Errno::EACCES => e
+        Sentry.capture_exception(e)
+        Rails.logger.error("clean_container_workspace: Got #{e.class}: #{e}")
       end
 
       # Checks only if container assignment is not nil and not whether the container itself is still present.
@@ -246,11 +246,11 @@ class DockerClient
     elsif container
       DockerContainerPool.destroy_container(container)
     end
-  rescue Docker::Error::NotFoundError => error
-    Rails.logger.error('destroy_container: Rescued from Docker::Error::NotFoundError: ' + error.to_s)
+  rescue Docker::Error::NotFoundError => e
+    Rails.logger.error("destroy_container: Rescued from Docker::Error::NotFoundError: #{e}")
     Rails.logger.error('No further actions are done concerning that.')
-  rescue Docker::Error::ConflictError => error
-    Rails.logger.error('destroy_container: Rescued from Docker::Error::ConflictError: ' + error.to_s)
+  rescue Docker::Error::ConflictError => e
+    Rails.logger.error("destroy_container: Rescued from Docker::Error::ConflictError: #{e}")
     Rails.logger.error('No further actions are done concerning that.')
   end
 
@@ -263,21 +263,22 @@ class DockerClient
   # only used by score and execute_arbitrary_command
   def execute_command(command, before_execution_block, output_consuming_block)
     # tries ||= 0
-    container_request_time = Time.now
+    container_request_time = Time.zone.now
     @container = DockerContainerPool.get_container(@execution_environment)
-    waiting_for_container_time = Time.now - container_request_time
+    waiting_for_container_time = Time.zone.now - container_request_time
     if @container
       @container.status = :executing
       before_execution_block.try(:call)
-      execution_request_time = Time.now
+      execution_request_time = Time.zone.now
       command_result = send_command(command, @container, &output_consuming_block)
-      container_execution_time = Time.now - execution_request_time
+      container_execution_time = Time.zone.now - execution_request_time
 
-      command_result.merge!(waiting_for_container_time: waiting_for_container_time)
-      command_result.merge!(container_execution_time: container_execution_time)
+      command_result[:waiting_for_container_time] = waiting_for_container_time
+      command_result[:container_execution_time] = container_execution_time
       command_result
     else
-      {status: :container_depleted, waiting_for_container_time: waiting_for_container_time, container_execution_time: nil}
+      {status: :container_depleted, waiting_for_container_time: waiting_for_container_time,
+container_execution_time: nil}
     end
   rescue Excon::Errors::SocketError => e
     # socket errors seems to be normal when using exec
@@ -298,7 +299,7 @@ class DockerClient
         # Prevent catching this error here
         raise
       rescue StandardError => e
-        Rails.logger.error('execute_websocket_command: Rescued from StandardError caused by before_execution_block.call: ' + e.to_s)
+        Rails.logger.error("execute_websocket_command: Rescued from StandardError caused by before_execution_block.call: #{e}")
       end
       # TODO: catch exception if socket could not be created
       @socket ||= create_socket(@container)
@@ -309,16 +310,16 @@ class DockerClient
   end
 
   def kill_after_timeout(container)
-    """
+    "
     We need to start a second thread to kill the websocket connection,
     as it is impossible to determine whether further input is requested.
-    """
+    "
     container.status = :executing
     @thread = Thread.new do
-      timeout = (@execution_environment.permitted_execution_time.to_i)  # seconds
+      timeout = @execution_environment.permitted_execution_time.to_i # seconds
       sleep(timeout)
       if container && container.status != :available
-        Rails.logger.info('Killing container after timeout of ' + timeout.to_s + ' seconds.')
+        Rails.logger.info("Killing container after timeout of #{timeout} seconds.")
         # send timeout to the tubesock socket
         # FIXME: 2nd thread to notify user.
         @tubesock&.send_data JSON.dump({'cmd' => 'timeout'})
@@ -338,7 +339,7 @@ class DockerClient
           ActiveRecord::Base.connection_pool.release_connection
         end
       else
-        Rails.logger.info('Container' + container.to_s + ' already removed.')
+        Rails.logger.info("Container#{container} already removed.")
       end
     ensure
       # guarantee that the thread is releasing the DB connection after it is done
@@ -351,25 +352,30 @@ class DockerClient
   end
 
   def exit_container(container)
-    Rails.logger.debug('exiting container ' + container.to_s)
+    Rails.logger.debug("exiting container #{container}")
     # exit the timeout thread if it is still alive
     exit_thread_if_alive
     @socket.close
     # if we use pooling and recylce the containers, put it back. otherwise, destroy it.
-    DockerContainerPool.config[:active] && RECYCLE_CONTAINERS ? self.class.return_container(container, @execution_environment) : self.class.destroy_container(container)
+    if DockerContainerPool.config[:active] && RECYCLE_CONTAINERS
+      self.class.return_container(container,
+        @execution_environment)
+    else
+      self.class.destroy_container(container)
+    end
   end
 
   def kill_container(container, _create_new = true)
     exit_thread_if_alive
-    Rails.logger.info('killing container ' + container.to_s)
+    Rails.logger.info("killing container #{container}")
     self.class.destroy_container(container)
   end
 
   def execute_run_command(submission, filename, &block)
-    """
+    "
     Run commands by attaching a websocket to Docker.
-    """
-    filepath = submission.collect_files.find { |f| f.name_with_extension == filename }.filepath
+    "
+    filepath = submission.collect_files.find {|f| f.name_with_extension == filename }.filepath
     command = submission.execution_environment.run_command % command_substitutions(filepath)
     create_workspace_files = proc { create_workspace_files(container, submission) }
     open_websocket_connection(command, create_workspace_files, block)
@@ -377,15 +383,15 @@ class DockerClient
   end
 
   def execute_test_command(submission, filename, &block)
-    """
+    "
     Stick to existing Docker API with exec command.
-    """
-    file = submission.collect_files.find { |f| f.name_with_extension == filename }
+    "
+    file = submission.collect_files.find {|f| f.name_with_extension == filename }
     filepath = file.filepath
     command = submission.execution_environment.test_command % command_substitutions(filepath)
     create_workspace_files = proc { create_workspace_files(container, submission) }
     test_result = execute_command(command, create_workspace_files, block)
-    test_result.merge!(file_role: file.role)
+    test_result[:file_role] = file.role
     test_result
   end
 
@@ -404,7 +410,7 @@ class DockerClient
   end
 
   def self.image_tags
-    Docker::Image.all.map { |image| image.info['RepoTags'] }.flatten.reject { |tag| tag.nil? || tag.include?('<none>') }
+    Docker::Image.all.map {|image| image.info['RepoTags'] }.flatten.reject {|tag| tag.nil? || tag.include?('<none>') }
   end
 
   def initialize(options = {})
@@ -417,7 +423,7 @@ class DockerClient
 
   def self.initialize_environment
     # TODO: Move to DockerContainerPool
-    raise(Error, 'Docker configuration missing!') unless config[:connection_timeout] && config[:workspace_root]
+    raise Error.new('Docker configuration missing!') unless config[:connection_timeout] && config[:workspace_root]
 
     Docker.url = config[:host] if config[:host]
     # TODO: availability check disabled for performance reasons. Reconsider if this is necessary.
@@ -427,11 +433,13 @@ class DockerClient
   end
 
   def local_file_path(options = {})
-    resulting_file_path = File.join(self.class.local_workspace_path(options[:container]), options[:file].path || '', options[:file].name_with_extension)
+    resulting_file_path = File.join(self.class.local_workspace_path(options[:container]), options[:file].path || '',
+      options[:file].name_with_extension)
     absolute_path = File.expand_path(resulting_file_path)
     unless absolute_path.start_with? self.class.local_workspace_path(options[:container]).to_s
-      raise(FilepathError, 'Filepath not allowed')
+      raise FilepathError.new('Filepath not allowed')
     end
+
     absolute_path
   end
 
@@ -457,12 +465,12 @@ class DockerClient
   end
 
   def self.return_container(container, execution_environment)
-    Rails.logger.debug('returning container ' + container.to_s)
+    Rails.logger.debug("returning container #{container}")
     begin
       clean_container_workspace(container)
-    rescue Docker::Error::NotFoundError => error
+    rescue Docker::Error::NotFoundError => e
       # FIXME: Create new container?
-      Rails.logger.info('return_container: Rescued from Docker::Error::NotFoundError: ' + error.to_s)
+      Rails.logger.info("return_container: Rescued from Docker::Error::NotFoundError: #{e}")
       Rails.logger.info('Nothing is done here additionally. The container will be exchanged upon its next retrieval.')
     end
     DockerContainerPool.return_container(container, execution_environment)
@@ -477,21 +485,30 @@ class DockerClient
     Timeout.timeout(@execution_environment.permitted_execution_time.to_i) do
       # TODO: check phusion doku again if we need -i -t options here
       # https://stackoverflow.com/questions/363223/how-do-i-get-both-stdout-and-stderr-to-go-to-the-terminal-and-a-log-file
-      output = container.exec(['bash', '-c',  "#{command} 1> >(tee -a /tmp/stdout.log) 2> >(tee -a /tmp/stderr.log >&2); rm -f /tmp/std*.log"], tty: false)
+      output = container.exec(
+        ['bash', '-c',
+         "#{command} 1> >(tee -a /tmp/stdout.log) 2> >(tee -a /tmp/stderr.log >&2); rm -f /tmp/std*.log"], tty: false
+      )
     end
     Rails.logger.debug 'output from container.exec'
     Rails.logger.debug output
     if output.nil?
       kill_container(container)
     else
-      result = {status: output[2] == 0 ? :ok : :failed, stdout: output[0].join.force_encoding('utf-8'), stderr: output[1].join.force_encoding('utf-8')}
+      result = {status: (output[2]).zero? ? :ok : :failed, stdout: output[0].join.force_encoding('utf-8'),
+stderr: output[1].join.force_encoding('utf-8')}
     end
 
     # if we use pooling and recylce the containers, put it back. otherwise, destroy it.
-    DockerContainerPool.config[:active] && RECYCLE_CONTAINERS ? self.class.return_container(container, @execution_environment) : self.class.destroy_container(container)
+    if DockerContainerPool.config[:active] && RECYCLE_CONTAINERS
+      self.class.return_container(container,
+        @execution_environment)
+    else
+      self.class.destroy_container(container)
+    end
     result
   rescue Timeout::Error
-    Rails.logger.info('got timeout error for container ' + container.to_s)
+    Rails.logger.info("got timeout error for container #{container}")
     stdout = container.exec(['cat', '/tmp/stdout.log'])[0].join.force_encoding('utf-8')
     stderr = container.exec(['cat', '/tmp/stderr.log'])[0].join.force_encoding('utf-8')
     kill_container(container)
@@ -501,5 +518,6 @@ class DockerClient
   private :send_command
 
   class Error < RuntimeError; end
+
   class FilepathError < RuntimeError; end
 end
diff --git a/lib/docker_container_mixin.rb b/lib/docker_container_mixin.rb
index 2a5d60f7..83b77865 100644
--- a/lib/docker_container_mixin.rb
+++ b/lib/docker_container_mixin.rb
@@ -1,10 +1,7 @@
-module DockerContainerMixin
+# frozen_string_literal: true
 
-  attr_accessor :start_time
-  attr_accessor :status
-  attr_accessor :re_use
-  attr_accessor :execution_environment
-  attr_accessor :docker_client
+module DockerContainerMixin
+  attr_accessor :start_time, :status, :re_use, :execution_environment, :docker_client
 
   def binds
     host_config['Binds']
@@ -12,7 +9,7 @@ module DockerContainerMixin
 
   def port_bindings
     # Don't use cached version as this might be changed during runtime
-    json['HostConfig']['PortBindings'].try(:map) { |key, value| [key.to_i, value.first['HostPort'].to_i] }.to_h
+    json['HostConfig']['PortBindings'].try(:map) {|key, value| [key.to_i, value.first['HostPort'].to_i] }.to_h
   end
 
   def host_config
diff --git a/lib/docker_container_pool.rb b/lib/docker_container_pool.rb
index abddb49d..fd3d85c1 100644
--- a/lib/docker_container_pool.rb
+++ b/lib/docker_container_pool.rb
@@ -1,30 +1,32 @@
+# frozen_string_literal: true
+
 require 'concurrent/future'
 require 'concurrent/timer_task'
 
-
 class DockerContainerPool
-
   def self.config
-    #TODO: Why erb?
+    # TODO: Why erb?
     @config ||= CodeOcean::Config.new(:docker).read(erb: true)[:pool]
   end
 
   def self.create_container(execution_environment)
-    Rails.logger.info('trying to create container for execution environment: ' + execution_environment.to_s)
+    Rails.logger.info("trying to create container for execution environment: #{execution_environment}")
     container = DockerClient.create_container(execution_environment)
     container.status = 'available' # FIXME: String vs Symbol usage?
-    #Rails.logger.debug('created container ' + container.to_s + ' for execution environment ' + execution_environment.to_s)
+    # Rails.logger.debug('created container ' + container.to_s + ' for execution environment ' + execution_environment.to_s)
     container
   rescue StandardError => e
-    Sentry.set_extras({container: container.inspect, execution_environment: execution_environment.inspect, config: config.inspect})
+    Sentry.set_extras({container: container.inspect, execution_environment: execution_environment.inspect,
+config: config.inspect})
     Sentry.capture_exception(e)
     nil
   end
 
   def self.return_container(container, execution_environment)
-    Faraday.get(config[:location] + "/docker_container_pool/return_container/" + container.id)
+    Faraday.get("#{config[:location]}/docker_container_pool/return_container/#{container.id}")
   rescue StandardError => e
-    Sentry.set_extras({container: container.inspect, execution_environment: execution_environment.inspect, config: config.inspect})
+    Sentry.set_extras({container: container.inspect, execution_environment: execution_environment.inspect,
+config: config.inspect})
     Sentry.capture_exception(e)
     nil
   end
@@ -33,10 +35,11 @@ class DockerContainerPool
     # if pooling is active, do pooling, otherwise just create an container and return it
     if config[:active]
       begin
-        container_id = JSON.parse(Faraday.get(config[:location] + "/docker_container_pool/get_container/" + execution_environment.id.to_s).body)['id']
-        Docker::Container.get(container_id) unless container_id.blank?
+        container_id = JSON.parse(Faraday.get("#{config[:location]}/docker_container_pool/get_container/#{execution_environment.id}").body)['id']
+        Docker::Container.get(container_id) if container_id.present?
       rescue StandardError => e
-        Sentry.set_extras({container_id: container_id.inspect, execution_environment: execution_environment.inspect, config: config.inspect})
+        Sentry.set_extras({container_id: container_id.inspect, execution_environment: execution_environment.inspect,
+config: config.inspect})
         Sentry.capture_exception(e)
         nil
       end
@@ -46,11 +49,11 @@ class DockerContainerPool
   end
 
   def self.destroy_container(container)
-    Faraday.get(config[:location] + "/docker_container_pool/destroy_container/" + container.id)
+    Faraday.get("#{config[:location]}/docker_container_pool/destroy_container/#{container.id}")
   end
 
   def self.quantities
-    response = JSON.parse(Faraday.get(config[:location] + "/docker_container_pool/quantities").body)
+    response = JSON.parse(Faraday.get("#{config[:location]}/docker_container_pool/quantities").body)
     response.transform_keys(&:to_i)
   rescue StandardError => e
     Sentry.set_extras({response: response.inspect})
@@ -59,7 +62,7 @@ class DockerContainerPool
   end
 
   def self.dump_info
-    JSON.parse(Faraday.get(config[:location] + "/docker_container_pool/dump_info").body)
+    JSON.parse(Faraday.get("#{config[:location]}/docker_container_pool/dump_info").body)
   rescue StandardError => e
     Sentry.capture_exception(e)
     nil
diff --git a/lib/file_tree.rb b/lib/file_tree.rb
index ced4ea45..672ceab8 100644
--- a/lib/file_tree.rb
+++ b/lib/file_tree.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class FileTree < Tree::TreeNode
   def file_icon(file)
     if file.file_type.audio?
@@ -25,10 +27,10 @@ class FileTree < Tree::TreeNode
 
   def initialize(files = [])
     super(root_label)
-    files.uniq{|f| f.name_with_extension}.each do |file|
+    files.uniq(&:name_with_extension).each do |file|
       parent = self
       (file.path || '').split('/').each do |segment|
-        node = parent.children.detect { |child| child.name == segment } || parent.add(Tree::TreeNode.new(segment))
+        node = parent.children.detect {|child| child.name == segment } || parent.add(Tree::TreeNode.new(segment))
         parent = node
       end
       parent.add(Tree::TreeNode.new(file.name_with_extension, file))
@@ -37,14 +39,14 @@ class FileTree < Tree::TreeNode
 
   def map_to_js_tree(node)
     {
-      children: node.children.map { |child| map_to_js_tree(child) },
+      children: node.children.map {|child| map_to_js_tree(child) },
       icon: node_icon(node),
       id: node.content.try(:ancestor_id),
       state: {
         disabled: !node.is_leaf?,
-        opened: !node.is_leaf?
+        opened: !node.is_leaf?,
       },
-      text: node.name
+      text: node.name,
     }
   end
   private :map_to_js_tree
@@ -68,8 +70,8 @@ class FileTree < Tree::TreeNode
   def to_js_tree
     {
       core: {
-        data: map_to_js_tree(self)
-      }
+        data: map_to_js_tree(self),
+      },
     }.to_json
   end
 end
diff --git a/lib/generators/testing_framework_adapter_generator.rb b/lib/generators/testing_framework_adapter_generator.rb
index 34de7ff4..9b113fe8 100644
--- a/lib/generators/testing_framework_adapter_generator.rb
+++ b/lib/generators/testing_framework_adapter_generator.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails/generators'
 
 class TestingFrameworkAdapterGenerator < Rails::Generators::NamedBase
@@ -5,26 +7,26 @@ class TestingFrameworkAdapterGenerator < Rails::Generators::NamedBase
   SPEC_PATH = ->(name) { Rails.root.join('spec', 'lib', "#{name.underscore}_adapter_spec.rb") }
 
   def create_testing_framework_adapter
-    create_file ADAPTER_PATH.call(file_name), <<-code
-class #{file_name.camelize}Adapter < TestingFrameworkAdapter
-  def self.framework_name
-    '#{file_name.camelize}'
-  end
-
-  def parse_output(output)
-  end
-end
-    code
+    create_file ADAPTER_PATH.call(file_name), <<~CODE
+            class #{file_name.camelize}Adapter < TestingFrameworkAdapter
+              def self.framework_name
+                '#{file_name.camelize}'
+              end
+      #{'      '}
+              def parse_output(output)
+              end
+            end
+    CODE
   end
 
   def create_spec
-    create_file SPEC_PATH.call(file_name), <<-code
-require 'rails_helper'
-
-describe #{file_name.camelize}Adapter do
-  describe '#parse_output' do
-  end
-end
-    code
+    create_file SPEC_PATH.call(file_name), <<~CODE
+            require 'rails_helper'
+      #{'      '}
+            describe #{file_name.camelize}Adapter do
+              describe '#parse_output' do
+              end
+            end
+    CODE
   end
 end
diff --git a/lib/junit_adapter.rb b/lib/junit_adapter.rb
index df0eff5d..a7eb31c1 100644
--- a/lib/junit_adapter.rb
+++ b/lib/junit_adapter.rb
@@ -1,8 +1,10 @@
+# frozen_string_literal: true
+
 class JunitAdapter < TestingFrameworkAdapter
-  COUNT_REGEXP = /Tests run: (\d+)/
-  FAILURES_REGEXP = /Failures: (\d+)/
-  SUCCESS_REGEXP = /OK \((\d+) test[s]?\)/
-  ASSERTION_ERROR_REGEXP = /java\.lang\.AssertionError:?\s(.*?)\tat org.junit|org\.junit\.ComparisonFailure:\s(.*?)\tat org.junit/m
+  COUNT_REGEXP = /Tests run: (\d+)/.freeze
+  FAILURES_REGEXP = /Failures: (\d+)/.freeze
+  SUCCESS_REGEXP = /OK \((\d+) tests?\)/.freeze
+  ASSERTION_ERROR_REGEXP = /java\.lang\.AssertionError:?\s(.*?)\tat org.junit|org\.junit\.ComparisonFailure:\s(.*?)\tat org.junit/m.freeze
 
   def self.framework_name
     'JUnit'
diff --git a/lib/mocha_adapter.rb b/lib/mocha_adapter.rb
index a5b8469d..7d5bb7b3 100644
--- a/lib/mocha_adapter.rb
+++ b/lib/mocha_adapter.rb
@@ -1,6 +1,8 @@
+# frozen_string_literal: true
+
 class MochaAdapter < TestingFrameworkAdapter
-  SUCCESS_REGEXP = /(\d+) passing/
-  FAILURES_REGEXP = /(\d+) failing/
+  SUCCESS_REGEXP = /(\d+) passing/.freeze
+  FAILURES_REGEXP = /(\d+) failing/.freeze
 
   def self.framework_name
     'Mocha'
@@ -11,6 +13,6 @@ class MochaAdapter < TestingFrameworkAdapter
     matches_failed = FAILURES_REGEXP.match(output[:stdout])
     failed = matches_failed ? matches_failed.captures.first.to_i : 0
     success = matches_success ? matches_success.captures.first.to_i : 0
-    {count: success+failed, failed: failed}
+    {count: success + failed, failed: failed}
   end
 end
diff --git a/lib/nonce_store.rb b/lib/nonce_store.rb
index 5b1b57c0..6f49ffde 100644
--- a/lib/nonce_store.rb
+++ b/lib/nonce_store.rb
@@ -1,10 +1,12 @@
+# frozen_string_literal: true
+
 class NonceStore
   def self.build_cache_key(nonce)
     "lti_nonce_#{nonce}"
   end
 
   def self.add(nonce)
-    Rails.cache.write(build_cache_key(nonce), Time.now, expires_in: Lti::MAXIMUM_SESSION_AGE)
+    Rails.cache.write(build_cache_key(nonce), Time.zone.now, expires_in: Lti::MAXIMUM_SESSION_AGE)
   end
 
   def self.delete(nonce)
diff --git a/lib/port_pool.rb b/lib/port_pool.rb
index 4a493df9..e32b5438 100644
--- a/lib/port_pool.rb
+++ b/lib/port_pool.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class PortPool
   PORT_RANGE = DockerClient.config[:ports]
 
@@ -11,6 +13,6 @@ class PortPool
   end
 
   def self.release(port)
-    @available_ports << port if PORT_RANGE.include?(port) && !@available_ports.include?(port)
+    @available_ports << port if PORT_RANGE.include?(port) && @available_ports.exclude?(port)
   end
 end
diff --git a/lib/prometheus/controller.rb b/lib/prometheus/controller.rb
index 19bcc931..0ef27f00 100644
--- a/lib/prometheus/controller.rb
+++ b/lib/prometheus/controller.rb
@@ -42,11 +42,11 @@ module Prometheus
       def initialize_rfc_metrics
         # Initialize rfc metric
         @rfc_count.observe(RequestForComment.unsolved.where(full_score_reached: false).count,
-                           state: RequestForComment::ONGOING)
+          state: RequestForComment::ONGOING)
         @rfc_count.observe(RequestForComment.unsolved.where(full_score_reached: true).count,
-                           state: RequestForComment::SOFT_SOLVED)
+          state: RequestForComment::SOFT_SOLVED)
         @rfc_count.observe(RequestForComment.where(solved: true).count,
-                           state: RequestForComment::SOLVED)
+          state: RequestForComment::SOLVED)
 
         # count of rfcs with comments
         @rfc_commented_count.observe(RequestForComment.joins(:comments).distinct.count(:id))
@@ -56,8 +56,8 @@ module Prometheus
         Rails.logger.debug("Prometheus metric updated for #{object.class.name}")
 
         case object
-        when RequestForComment
-          update_rfc(object)
+          when RequestForComment
+            update_rfc(object)
         end
       end
 
@@ -66,10 +66,10 @@ module Prometheus
         Rails.logger.debug("Prometheus instance count increased for #{object.class.name}")
 
         case object
-        when RequestForComment
-          create_rfc(object)
-        when Comment
-          create_comment(object)
+          when RequestForComment
+            create_rfc(object)
+          when Comment
+            create_comment(object)
         end
       end
 
@@ -78,8 +78,8 @@ module Prometheus
         Rails.logger.debug("Prometheus instance count decreased for #{object.class.name}")
 
         case object
-        when Comment
-          destroy_comment(object)
+          when Comment
+            destroy_comment(object)
         end
       end
 
diff --git a/lib/py_lint_adapter.rb b/lib/py_lint_adapter.rb
index d7d8c133..575c0b44 100644
--- a/lib/py_lint_adapter.rb
+++ b/lib/py_lint_adapter.rb
@@ -1,6 +1,8 @@
+# frozen_string_literal: true
+
 class PyLintAdapter < TestingFrameworkAdapter
-  REGEXP = /Your code has been rated at (-?\d+\.?\d*)\/(\d+\.?\d*)/
-  ASSERTION_ERROR_REGEXP = /^(.*?\.py):(\d+):(.*?)\(([^,]*?), ([^,]*?),([^,]*?)\) (.*?)$/
+  REGEXP = %r{Your code has been rated at (-?\d+\.?\d*)/(\d+\.?\d*)}.freeze
+  ASSERTION_ERROR_REGEXP = /^(.*?\.py):(\d+):(.*?)\(([^,]*?), ([^,]*?),([^,]*?)\) (.*?)$/.freeze
 
   def self.framework_name
     'PyLint'
@@ -22,14 +24,14 @@ class PyLintAdapter < TestingFrameworkAdapter
       assertion_error_matches = Timeout.timeout(2.seconds) do
         output[:stdout].scan(ASSERTION_ERROR_REGEXP).map do |match|
           {
-              file_name: match[0].strip,
+            file_name: match[0].strip,
               line: match[1].to_i,
               severity: match[2].strip,
               code: match[3].strip,
               name: match[4].strip,
               # e.g. function name, nil if outside of a function. Not always available
               scope: match[5].strip.presence,
-              result: match[6].strip
+              result: match[6].strip,
           }
         end || []
       end
@@ -37,8 +39,9 @@ class PyLintAdapter < TestingFrameworkAdapter
       Sentry.capture_message({stdout: output[:stdout], regex: ASSERTION_ERROR_REGEXP}.to_json)
       assertion_error_matches = []
     end
-    concatenated_errors = assertion_error_matches.map { |result| "#{result[:name]}: #{result[:result]}" }.flatten
-    {count: count, failed: failed, error_messages: concatenated_errors, detailed_linter_results: assertion_error_matches}
+    concatenated_errors = assertion_error_matches.map {|result| "#{result[:name]}: #{result[:result]}" }.flatten
+    {count: count, failed: failed, error_messages: concatenated_errors,
+detailed_linter_results: assertion_error_matches}
   end
 
   def self.translate_linter(assessment, locale)
@@ -47,7 +50,7 @@ class PyLintAdapter < TestingFrameworkAdapter
 
     I18n.locale = locale || I18n.default_locale
 
-    return assessment unless assessment[:detailed_linter_results].present?
+    return assessment if assessment[:detailed_linter_results].blank?
 
     assessment[:detailed_linter_results].map! do |message|
       severity = message[:severity]
@@ -73,7 +76,7 @@ class PyLintAdapter < TestingFrameworkAdapter
         replacement = {}
       end
 
-      replacement.merge!(default: message[:result])
+      replacement[:default] = message[:result]
       message[:result] = I18n.t("linter.#{severity}.#{name}.replacement", replacement)
       message
     end
diff --git a/lib/py_unit_adapter.rb b/lib/py_unit_adapter.rb
index 30528c32..88f43758 100644
--- a/lib/py_unit_adapter.rb
+++ b/lib/py_unit_adapter.rb
@@ -1,8 +1,10 @@
+# frozen_string_literal: true
+
 class PyUnitAdapter < TestingFrameworkAdapter
-  COUNT_REGEXP = /Ran (\d+) test/
-  FAILURES_REGEXP = /FAILED \(.*failures=(\d+).*\)/
-  ERRORS_REGEXP = /FAILED \(.*errors=(\d+).*\)/
-  ASSERTION_ERROR_REGEXP = /^(ERROR|FAIL):\ (.*?)\ .*?^[^\.\n]*?(Error|Exception):\s((\s|\S)*?)(>>>.*?)*\s\s(-|=){70}/m
+  COUNT_REGEXP = /Ran (\d+) test/.freeze
+  FAILURES_REGEXP = /FAILED \(.*failures=(\d+).*\)/.freeze
+  ERRORS_REGEXP = /FAILED \(.*errors=(\d+).*\)/.freeze
+  ASSERTION_ERROR_REGEXP = /^(ERROR|FAIL):\ (.*?)\ .*?^[^.\n]*?(Error|Exception):\s((\s|\S)*?)(>>>.*?)*\s\s(-|=){70}/m.freeze
 
   def self.framework_name
     'PyUnit'
@@ -16,7 +18,7 @@ class PyUnitAdapter < TestingFrameworkAdapter
     errors = error_matches ? error_matches.captures.try(:first).to_i : 0
     begin
       assertion_error_matches = Timeout.timeout(2.seconds) do
-        output[:stderr].scan(ASSERTION_ERROR_REGEXP).map { |match|
+        output[:stderr].scan(ASSERTION_ERROR_REGEXP).map do |match|
           testname = match[1]
           error = match[3].strip
 
@@ -25,7 +27,7 @@ class PyUnitAdapter < TestingFrameworkAdapter
           else
             "#{testname}: #{error}"
           end
-        }.flatten || []
+        end.flatten || []
       end
     rescue Timeout::Error
       Sentry.capture_message({stderr: output[:stderr], regex: ASSERTION_ERROR_REGEXP}.to_json)
diff --git a/lib/py_unit_and_py_lint_adapter.rb b/lib/py_unit_and_py_lint_adapter.rb
index bdac31c4..f303a7d1 100644
--- a/lib/py_unit_and_py_lint_adapter.rb
+++ b/lib/py_unit_and_py_lint_adapter.rb
@@ -1,5 +1,6 @@
-class PyUnitAndPyLintAdapter < TestingFrameworkAdapter
+# frozen_string_literal: true
 
+class PyUnitAndPyLintAdapter < TestingFrameworkAdapter
   def self.framework_name
     'PyUnit and PyLint'
   end
diff --git a/lib/python20_course_week.rb b/lib/python20_course_week.rb
index 7d510ea6..0d4d9bc7 100644
--- a/lib/python20_course_week.rb
+++ b/lib/python20_course_week.rb
@@ -1,22 +1,21 @@
 # frozen_string_literal: true
 
 class Python20CourseWeek
-
   def self.get_for(exercise)
     case exercise.title
-    when /Python20 Aufgabe 1/
-      1
-    when /Python20 Aufgabe 2/
-      2
-    when /Python20 Aufgabe 3/
-      3
-    when /Python20 Aufgabe 4/
-      4
-    when /Python20 Snake/
-      4
-    else
-      # Not part of the Python20 course
-      nil
+      when /Python20 Aufgabe 1/
+        1
+      when /Python20 Aufgabe 2/
+        2
+      when /Python20 Aufgabe 3/
+        3
+      when /Python20 Aufgabe 4/
+        4
+      when /Python20 Snake/
+        4
+      else
+        # Not part of the Python20 course
+        nil
     end
   end
 
diff --git a/lib/r_script_adapter.rb b/lib/r_script_adapter.rb
index d387eaa2..bd65af51 100644
--- a/lib/r_script_adapter.rb
+++ b/lib/r_script_adapter.rb
@@ -1,6 +1,8 @@
+# frozen_string_literal: true
+
 class RScriptAdapter < TestingFrameworkAdapter
-  REGEXP = /(\d+) examples?, (\d+) passed?/
-  ASSERTION_ERROR_REGEXP = /AssertionError:\s(.*)/
+  REGEXP = /(\d+) examples?, (\d+) passed?/.freeze
+  ASSERTION_ERROR_REGEXP = /AssertionError:\s(.*)/.freeze
 
   def self.framework_name
     'R Script'
diff --git a/lib/rspec_adapter.rb b/lib/rspec_adapter.rb
index c68a0e2d..80d8a4d6 100644
--- a/lib/rspec_adapter.rb
+++ b/lib/rspec_adapter.rb
@@ -1,5 +1,7 @@
+# frozen_string_literal: true
+
 class RspecAdapter < TestingFrameworkAdapter
-  REGEXP = /(\d+) examples?, (\d+) failures?/
+  REGEXP = /(\d+) examples?, (\d+) failures?/.freeze
 
   def self.framework_name
     'RSpec 3'
diff --git a/lib/seeds_helper.rb b/lib/seeds_helper.rb
index fa506bc8..817862eb 100644
--- a/lib/seeds_helper.rb
+++ b/lib/seeds_helper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module SeedsHelper
   def self.read_seed_file(filename)
     file = File.new(seed_file_path(filename), 'r')
diff --git a/lib/sql_result_set_comparator_adapter.rb b/lib/sql_result_set_comparator_adapter.rb
index 61b9ae3d..3607586a 100644
--- a/lib/sql_result_set_comparator_adapter.rb
+++ b/lib/sql_result_set_comparator_adapter.rb
@@ -1,6 +1,8 @@
+# frozen_string_literal: true
+
 class SqlResultSetComparatorAdapter < TestingFrameworkAdapter
-  MISSING_TUPLES_REGEXP = /Missing tuples: \[\]/
-  UNEXPECTED_TUPLES_REGEXP = /Unexpected tuples: \[\]/
+  MISSING_TUPLES_REGEXP = /Missing tuples: \[\]/.freeze
+  UNEXPECTED_TUPLES_REGEXP = /Unexpected tuples: \[\]/.freeze
 
   def self.framework_name
     'SqlResultSetComparator'
diff --git a/lib/tasks/detect_exercise_anomalies.rake b/lib/tasks/detect_exercise_anomalies.rake
index ba27cf4f..cb0ca5f1 100644
--- a/lib/tasks/detect_exercise_anomalies.rake
+++ b/lib/tasks/detect_exercise_anomalies.rake
@@ -111,7 +111,7 @@ namespace :detect_exercise_anomalies do
   end
 
   def notify_users(collection, anomalies)
-    by_id_and_type = proc { |u| {user_id: u[:user_id], user_type: u[:user_type]} }
+    by_id_and_type = proc {|u| {user_id: u[:user_id], user_type: u[:user_type]} }
 
     log('Sending E-Mails to best and worst performing users of each anomaly...', 2)
     anomalies.each do |exercise_id, average_working_time|
@@ -122,7 +122,7 @@ namespace :detect_exercise_anomalies do
       users = {}
       %i[performers_by_time performers_by_score].each do |method|
         # merge users found by multiple methods returning a hash {best: [], worst: []}
-        users = users.merge(send(method, exercise, NUMBER_OF_USERS_PER_CLASS)) { |_key, this, other| this + other }
+        users = users.merge(send(method, exercise, NUMBER_OF_USERS_PER_CLASS)) {|_key, this, other| this + other }
       end
 
       # write reasons for feedback emails to db
@@ -140,7 +140,8 @@ namespace :detect_exercise_anomalies do
       users_to_notify.each do |u|
         user = u[:user_type] == InternalUser.name ? InternalUser.find(u[:user_id]) : ExternalUser.find(u[:user_id])
         host = CodeOcean::Application.config.action_mailer.default_url_options[:host]
-        feedback_link = Rails.application.routes.url_helpers.url_for(action: :new, controller: :user_exercise_feedbacks, exercise_id: exercise.id, host: host)
+        feedback_link = Rails.application.routes.url_helpers.url_for(action: :new,
+controller: :user_exercise_feedbacks, exercise_id: exercise.id, host: host)
         UserMailer.exercise_anomaly_needs_feedback(user, exercise, feedback_link).deliver
       end
       log("Asked #{users_to_notify.size} users for feedback.", 2)
@@ -149,7 +150,7 @@ namespace :detect_exercise_anomalies do
 
   def performers_by_score(exercise, users)
     submissions = exercise.last_submission_per_user.where.not(score: nil).order(score: :desc)
-    map_block = proc { |item| {user_id: item.user_id, user_type: item.user_type, value: item.score, reason: 'score'} }
+    map_block = proc {|item| {user_id: item.user_id, user_type: item.user_type, value: item.score, reason: 'score'} }
     best_performers = submissions.first(users).to_a.map(&map_block)
     worst_performers = submissions.last(users).to_a.map(&map_block)
     {best: best_performers, worst: worst_performers}
@@ -161,8 +162,10 @@ namespace :detect_exercise_anomalies do
        value: time_to_f(item['working_time']), reason: 'time'}
     end
     avg_score = exercise.average_score
-    working_times.reject! { |item| item[:value].nil? or item[:value] <= MIN_USER_WORKING_TIME or item[:score] < avg_score }
-    working_times.sort_by! { |item| item[:value] }
+    working_times.reject! do |item|
+      item[:value].nil? or item[:value] <= MIN_USER_WORKING_TIME or item[:score] < avg_score
+    end
+    working_times.sort_by! {|item| item[:value] }
     {best: working_times.first(users), worst: working_times.last(users)}
   end
 
diff --git a/lib/tasks/docker.rake b/lib/tasks/docker.rake
index 5152429a..a0c89a89 100644
--- a/lib/tasks/docker.rake
+++ b/lib/tasks/docker.rake
@@ -1,6 +1,8 @@
+# frozen_string_literal: true
+
 namespace :docker do
   desc 'Remove all Docker containers and dangling Docker images (using the CLI)'
-  task :clean_up do
+  task clean_up: :environment do
     `test -n "$(docker ps --all --quiet)" && docker rm --force $(docker ps --all --quiet)`
     `test -n "docker images --filter dangling=true --quiet" && docker rmi $(docker images --filter dangling=true --quiet)`
   end
diff --git a/lib/tasks/write_displaynames.rake b/lib/tasks/write_displaynames.rake
index 955cd355..66129783 100644
--- a/lib/tasks/write_displaynames.rake
+++ b/lib/tasks/write_displaynames.rake
@@ -1,17 +1,17 @@
+# frozen_string_literal: true
+
 namespace :user do
-require 'csv'
+  require 'csv'
 
-desc 'write displaynames retrieved from the account service as csv into the codeocean database'
- 
-task :write_displaynames, [:file_path_read]  => [ :environment ] do |t, args|
+  desc 'write displaynames retrieved from the account service as csv into the codeocean database'
 
-   csv_input = CSV.read(args[:file_path_read], headers:true)
+  task :write_displaynames, [:file_path_read] => [:environment] do |_t, args|
+    csv_input = CSV.read(args[:file_path_read], headers: true)
 
     csv_input.each do |row|
-      user = ExternalUser.find_by(:external_id => row[0])
+      user = ExternalUser.find_by(external_id: row[0])
       puts "Change name from   #{user.name} to #{row[1]}"
       user.update(name: row[1])
     end
   end
 end
-
diff --git a/lib/testing_framework_adapter.rb b/lib/testing_framework_adapter.rb
index 895a5299..d2b20f33 100644
--- a/lib/testing_framework_adapter.rb
+++ b/lib/testing_framework_adapter.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class TestingFrameworkAdapter
   def augment_output(options = {})
     if !options[:count]
@@ -15,7 +17,7 @@ class TestingFrameworkAdapter
   end
 
   def parse_output(*)
-    fail(NotImplementedError, "#{self.class} should implement #parse_output!")
+    raise NotImplementedError.new("#{self.class} should implement #parse_output!")
   end
   private :parse_output
 
diff --git a/spec/concerns/file_parameters_spec.rb b/spec/concerns/file_parameters_spec.rb
index 73383045..65e209a2 100644
--- a/spec/concerns/file_parameters_spec.rb
+++ b/spec/concerns/file_parameters_spec.rb
@@ -19,7 +19,7 @@ describe FileParameters do
 
     describe 'accepts' do
       it 'main file of the exercise' do
-        main_file = hello_world.files.find { |e| e.role = 'main_file' }
+        main_file = hello_world.files.find {|e| e.role = 'main_file' }
         expect(file_accepted?(main_file)).to be true
       end
 
diff --git a/spec/concerns/lti_spec.rb b/spec/concerns/lti_spec.rb
index 801b4505..beff3298 100644
--- a/spec/concerns/lti_spec.rb
+++ b/spec/concerns/lti_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 class Controller < AnonymousController
@@ -31,7 +33,7 @@ describe Lti do
     let(:last_name) { 'Doe' }
     let(:full_name) { 'John Doe' }
     let(:provider) { double }
-    let(:provider_full) { double(:lis_person_name_full => full_name) }
+    let(:provider_full) { double(lis_person_name_full: full_name) }
 
     context 'when a full name is provided' do
       it 'returns the full name' do
@@ -61,7 +63,8 @@ describe Lti do
   describe '#return_to_consumer' do
     context 'with a return URL' do
       let(:consumer_return_url) { 'http://example.org' }
-      before(:each) { expect(controller).to receive(:params).and_return(launch_presentation_return_url: consumer_return_url) }
+
+      before { expect(controller).to receive(:params).and_return(launch_presentation_return_url: consumer_return_url) }
 
       it 'redirects to the tool consumer' do
         expect(controller).to receive(:redirect_to).with(consumer_return_url)
@@ -76,7 +79,7 @@ describe Lti do
     end
 
     context 'without a return URL' do
-      before(:each) do
+      before do
         expect(controller).to receive(:params).and_return({})
         expect(controller).to receive(:redirect_to).with(:root)
       end
@@ -101,7 +104,7 @@ describe Lti do
     let(:consumer) { FactoryBot.create(:consumer) }
     let(:score) { 0.5 }
     let(:submission) { FactoryBot.create(:submission) }
-    let!(:lti_parameter) { FactoryBot.create(:lti_parameter, consumers_id: consumer.id, external_users_id: submission.user_id, exercises_id: submission.exercise_id)}
+    let!(:lti_parameter) { FactoryBot.create(:lti_parameter, consumers_id: consumer.id, external_users_id: submission.user_id, exercises_id: submission.exercise_id) }
 
     context 'with an invalid score' do
       it 'raises an exception' do
@@ -112,7 +115,6 @@ describe Lti do
 
     context 'with an valid score' do
       context 'with a tool consumer' do
-
         context 'when grading is not supported' do
           it 'returns a corresponding status' do
             expect_any_instance_of(IMS::LTI::ToolProvider).to receive(:outcome_service?).and_return(false)
@@ -124,7 +126,7 @@ describe Lti do
         context 'when grading is supported' do
           let(:response) { double }
 
-          before(:each) do
+          before do
             expect_any_instance_of(IMS::LTI::ToolProvider).to receive(:outcome_service?).and_return(true)
             expect_any_instance_of(IMS::LTI::ToolProvider).to receive(:post_replace_result!).with(score).and_return(response)
             expect(response).to receive(:response_code).at_least(:once).and_return(200)
@@ -170,7 +172,7 @@ describe Lti do
       controller.send(:store_lti_session_data, consumer: FactoryBot.build(:consumer), parameters: parameters)
     end
 
-    it 'it creates an LtiParameter Object' do
+    it 'creates an LtiParameter Object' do
       before_count = LtiParameter.count
       controller.instance_variable_set(:@current_user, FactoryBot.create(:external_user))
       controller.instance_variable_set(:@exercise, FactoryBot.create(:fibonacci))
diff --git a/spec/concerns/submission_scoring_spec.rb b/spec/concerns/submission_scoring_spec.rb
index 62b29817..59b08312 100644
--- a/spec/concerns/submission_scoring_spec.rb
+++ b/spec/concerns/submission_scoring_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 class Controller < AnonymousController
@@ -6,11 +8,13 @@ end
 
 describe SubmissionScoring do
   let(:controller) { Controller.new }
+
   before(:all) { @submission = FactoryBot.create(:submission, cause: 'submit') }
-  before(:each) { controller.instance_variable_set(:@current_user, FactoryBot.create(:external_user)) }
+
+  before { controller.instance_variable_set(:@current_user, FactoryBot.create(:external_user)) }
 
   describe '#collect_test_results' do
-    after(:each) { controller.send(:collect_test_results, @submission) }
+    after { controller.send(:collect_test_results, @submission) }
 
     it 'executes every teacher-defined test file' do
       @submission.collect_files.select(&:teacher_defined_assessment?).each do |file|
@@ -20,7 +24,7 @@ describe SubmissionScoring do
   end
 
   describe '#score_submission' do
-    after(:each) { controller.score_submission(@submission) }
+    after { controller.score_submission(@submission) }
 
     it 'collects the test results' do
       expect(controller).to receive(:collect_test_results).and_return([])
diff --git a/spec/controllers/admin/dashboard_controller_spec.rb b/spec/controllers/admin/dashboard_controller_spec.rb
index 20265e16..55d4ede5 100644
--- a/spec/controllers/admin/dashboard_controller_spec.rb
+++ b/spec/controllers/admin/dashboard_controller_spec.rb
@@ -1,18 +1,20 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe Admin::DashboardController do
-  before(:each) { allow(controller).to receive(:current_user).and_return(FactoryBot.build(:admin)) }
+  before { allow(controller).to receive(:current_user).and_return(FactoryBot.build(:admin)) }
 
   describe 'GET #show' do
     describe 'with format HTML' do
-      before(:each) { get :show }
+      before { get :show }
 
       expect_status(200)
       expect_template(:show)
     end
 
     describe 'with format JSON' do
-      before(:each) { get :show, format: :json }
+      before { get :show, format: :json }
 
       expect_json
       expect_status(200)
diff --git a/spec/controllers/application_controller_spec.rb b/spec/controllers/application_controller_spec.rb
index e8fdfcf9..541c95a5 100644
--- a/spec/controllers/application_controller_spec.rb
+++ b/spec/controllers/application_controller_spec.rb
@@ -1,10 +1,13 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe ApplicationController do
   describe '#current_user' do
     context 'with an external user' do
       let(:external_user) { FactoryBot.create(:external_user) }
-      before(:each) { session[:external_user_id] = external_user.id }
+
+      before { session[:external_user_id] = external_user.id }
 
       it 'returns the external user' do
         expect(controller.current_user).to eq(external_user)
@@ -13,7 +16,8 @@ describe ApplicationController do
 
     context 'without an external user' do
       let(:internal_user) { FactoryBot.create(:teacher) }
-      before(:each) { login_user(internal_user) }
+
+      before { login_user(internal_user) }
 
       it 'returns the internal user' do
         expect(controller.current_user).to eq(internal_user)
@@ -22,7 +26,7 @@ describe ApplicationController do
   end
 
   describe '#render_not_authorized' do
-    before(:each) do
+    before do
       expect(controller).to receive(:welcome) { controller.send(:render_not_authorized) }
       get :welcome
     end
@@ -35,19 +39,19 @@ describe ApplicationController do
     let(:locale) { :de }
 
     context 'when specifying a locale' do
-      before(:each) { allow(session).to receive(:[]=).at_least(:once) }
+      before { allow(session).to receive(:[]=).at_least(:once) }
 
       context "using the 'custom_locale' parameter" do
         it 'overwrites the session' do
           expect(session).to receive(:[]=).with(:locale, locale.to_s)
-          get :welcome, params: { custom_locale: locale }
+          get :welcome, params: {custom_locale: locale}
         end
       end
 
       context "using the 'locale' parameter" do
         it 'overwrites the session' do
           expect(session).to receive(:[]=).with(:locale, locale.to_s)
-          get :welcome, params: { locale: locale }
+          get :welcome, params: {locale: locale}
         end
       end
     end
@@ -70,7 +74,7 @@ describe ApplicationController do
   end
 
   describe 'GET #welcome' do
-    before(:each) { get :welcome }
+    before { get :welcome }
 
     expect_status(200)
     expect_template(:welcome)
diff --git a/spec/controllers/code_ocean/files_controller_spec.rb b/spec/controllers/code_ocean/files_controller_spec.rb
index 7525c097..8097cd70 100644
--- a/spec/controllers/code_ocean/files_controller_spec.rb
+++ b/spec/controllers/code_ocean/files_controller_spec.rb
@@ -4,14 +4,16 @@ require 'rails_helper'
 
 describe CodeOcean::FilesController do
   let(:user) { FactoryBot.create(:admin) }
-  before(:each) { allow(controller).to receive(:current_user).and_return(user) }
+
+  before { allow(controller).to receive(:current_user).and_return(user) }
 
   describe 'POST #create' do
     let(:submission) { FactoryBot.create(:submission, user: user) }
 
     context 'with a valid file' do
-      let(:perform_request) { proc { post :create, params: { code_ocean_file: FactoryBot.build(:file, context: submission).attributes, format: :json } } }
-      before(:each) do
+      let(:perform_request) { proc { post :create, params: {code_ocean_file: FactoryBot.build(:file, context: submission).attributes, format: :json} } }
+
+      before do
         submission.exercise.update(allow_file_creation: true)
         perform_request.call
       end
@@ -27,9 +29,9 @@ describe CodeOcean::FilesController do
     end
 
     context 'with an invalid file' do
-      before(:each) do
+      before do
         submission.exercise.update(allow_file_creation: true)
-        post :create, params: { code_ocean_file: {context_id: submission.id, context_type: Submission}, format: :json }
+        post :create, params: {code_ocean_file: {context_id: submission.id, context_type: Submission}, format: :json}
       end
 
       expect_assigns(file: CodeOcean::File)
@@ -40,8 +42,9 @@ describe CodeOcean::FilesController do
 
   describe 'DELETE #destroy' do
     let(:exercise) { FactoryBot.create(:fibonacci) }
-    let(:perform_request) { proc { delete :destroy, params: { id: exercise.files.first.id } } }
-    before(:each) { perform_request.call }
+    let(:perform_request) { proc { delete :destroy, params: {id: exercise.files.first.id} } }
+
+    before { perform_request.call }
 
     expect_assigns(file: CodeOcean::File)
 
diff --git a/spec/controllers/consumers_controller_spec.rb b/spec/controllers/consumers_controller_spec.rb
index 7ce2c378..209503a5 100644
--- a/spec/controllers/consumers_controller_spec.rb
+++ b/spec/controllers/consumers_controller_spec.rb
@@ -1,14 +1,18 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe ConsumersController do
   let(:consumer) { FactoryBot.create(:consumer) }
   let(:user) { FactoryBot.create(:admin) }
-  before(:each) { allow(controller).to receive(:current_user).and_return(user) }
+
+  before { allow(controller).to receive(:current_user).and_return(user) }
 
   describe 'POST #create' do
     context 'with a valid consumer' do
-      let(:perform_request) { proc { post :create, params: { consumer: FactoryBot.attributes_for(:consumer) } } }
-      before(:each) { perform_request.call }
+      let(:perform_request) { proc { post :create, params: {consumer: FactoryBot.attributes_for(:consumer)} } }
+
+      before { perform_request.call }
 
       expect_assigns(consumer: Consumer)
 
@@ -20,7 +24,7 @@ describe ConsumersController do
     end
 
     context 'with an invalid consumer' do
-      before(:each) { post :create, params: { consumer: {} } }
+      before { post :create, params: {consumer: {}} }
 
       expect_assigns(consumer: Consumer)
       expect_status(200)
@@ -29,20 +33,20 @@ describe ConsumersController do
   end
 
   describe 'DELETE #destroy' do
-    before(:each) { delete :destroy, params: { id: consumer.id } }
+    before { delete :destroy, params: {id: consumer.id} }
 
     expect_assigns(consumer: Consumer)
 
     it 'destroys the consumer' do
       consumer = FactoryBot.create(:consumer)
-      expect { delete :destroy, params: { id: consumer.id } }.to change(Consumer, :count).by(-1)
+      expect { delete :destroy, params: {id: consumer.id} }.to change(Consumer, :count).by(-1)
     end
 
     expect_redirect(:consumers)
   end
 
   describe 'GET #edit' do
-    before(:each) { get :edit, params: { id: consumer.id } }
+    before { get :edit, params: {id: consumer.id} }
 
     expect_assigns(consumer: Consumer)
     expect_status(200)
@@ -51,7 +55,8 @@ describe ConsumersController do
 
   describe 'GET #index' do
     let!(:consumers) { FactoryBot.create_pair(:consumer) }
-    before(:each) { get :index }
+
+    before { get :index }
 
     expect_assigns(consumers: Consumer.all)
     expect_status(200)
@@ -59,7 +64,7 @@ describe ConsumersController do
   end
 
   describe 'GET #new' do
-    before(:each) { get :new }
+    before { get :new }
 
     expect_assigns(consumer: Consumer)
     expect_status(200)
@@ -67,7 +72,7 @@ describe ConsumersController do
   end
 
   describe 'GET #show' do
-    before(:each) { get :show, params: { id: consumer.id } }
+    before { get :show, params: {id: consumer.id} }
 
     expect_assigns(consumer: :consumer)
     expect_status(200)
@@ -76,14 +81,14 @@ describe ConsumersController do
 
   describe 'PUT #update' do
     context 'with a valid consumer' do
-      before(:each) { put :update, params: { consumer: FactoryBot.attributes_for(:consumer), id: consumer.id } }
+      before { put :update, params: {consumer: FactoryBot.attributes_for(:consumer), id: consumer.id} }
 
       expect_assigns(consumer: Consumer)
       expect_redirect(:consumer)
     end
 
     context 'with an invalid consumer' do
-      before(:each) { put :update, params: { consumer: {name: ''}, id: consumer.id } }
+      before { put :update, params: {consumer: {name: ''}, id: consumer.id} }
 
       expect_assigns(consumer: Consumer)
       expect_status(200)
diff --git a/spec/controllers/error_template_attributes_controller_spec.rb b/spec/controllers/error_template_attributes_controller_spec.rb
index d1cb3d4f..a80ee6a2 100644
--- a/spec/controllers/error_template_attributes_controller_spec.rb
+++ b/spec/controllers/error_template_attributes_controller_spec.rb
@@ -1,43 +1,46 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe ErrorTemplateAttributesController do
   let!(:error_template_attribute) { FactoryBot.create(:error_template_attribute) }
   let(:user) { FactoryBot.create(:admin) }
-  before(:each) { allow(controller).to receive(:current_user).and_return(user) }
 
-  it "should get index" do
+  before { allow(controller).to receive(:current_user).and_return(user) }
+
+  it 'gets index' do
     get :index
     expect(response.status).to eq(200)
     expect(assigns(:error_template_attributes)).not_to be_nil
   end
 
-  it "should get new" do
+  it 'gets new' do
     get :new
     expect(response.status).to eq(200)
   end
 
-  it "should create error_template_attribute" do
-    expect { post :create, params: { error_template_attribute: {  } } }.to change(ErrorTemplateAttribute, :count).by(1)
+  it 'creates error_template_attribute' do
+    expect { post :create, params: {error_template_attribute: {}} }.to change(ErrorTemplateAttribute, :count).by(1)
     expect(response).to redirect_to(error_template_attribute_path(assigns(:error_template_attribute)))
   end
 
-  it "should show error_template_attribute" do
-    get :show, params: { id: error_template_attribute }
+  it 'shows error_template_attribute' do
+    get :show, params: {id: error_template_attribute}
     expect(response.status).to eq(200)
   end
 
-  it "should get edit" do
-    get :edit, params: { id: error_template_attribute }
+  it 'gets edit' do
+    get :edit, params: {id: error_template_attribute}
     expect(response.status).to eq(200)
   end
 
-  it "should update error_template_attribute" do
-    patch :update, params: { id: error_template_attribute, error_template_attribute: FactoryBot.attributes_for(:error_template_attribute) }
+  it 'updates error_template_attribute' do
+    patch :update, params: {id: error_template_attribute, error_template_attribute: FactoryBot.attributes_for(:error_template_attribute)}
     expect(response).to redirect_to(error_template_attribute_path(assigns(:error_template_attribute)))
   end
 
-  it "should destroy error_template_attribute" do
-    expect { delete :destroy, params: { id: error_template_attribute } }.to change(ErrorTemplateAttribute, :count).by(-1)
+  it 'destroys error_template_attribute' do
+    expect { delete :destroy, params: {id: error_template_attribute} }.to change(ErrorTemplateAttribute, :count).by(-1)
     expect(response).to redirect_to(error_template_attributes_path)
   end
 end
diff --git a/spec/controllers/error_templates_controller_spec.rb b/spec/controllers/error_templates_controller_spec.rb
index 9f5da525..4f7dfbaa 100644
--- a/spec/controllers/error_templates_controller_spec.rb
+++ b/spec/controllers/error_templates_controller_spec.rb
@@ -1,43 +1,46 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe ErrorTemplatesController do
   let!(:error_template) { FactoryBot.create(:error_template) }
   let(:user) { FactoryBot.create(:admin) }
-  before(:each) { allow(controller).to receive(:current_user).and_return(user) }
 
-  it "should get index" do
+  before { allow(controller).to receive(:current_user).and_return(user) }
+
+  it 'gets index' do
     get :index
     expect(response.status).to eq(200)
     expect(assigns(:error_templates)).not_to be_nil
   end
 
-  it "should get new" do
+  it 'gets new' do
     get :new
     expect(response.status).to eq(200)
   end
 
-  it "should create error_template" do
-    expect { post :create, params: {error_template: { execution_environment_id: error_template.execution_environment.id } } }.to change(ErrorTemplate, :count).by(1)
+  it 'creates error_template' do
+    expect { post :create, params: {error_template: {execution_environment_id: error_template.execution_environment.id}} }.to change(ErrorTemplate, :count).by(1)
     expect(response).to redirect_to(error_template_path(assigns(:error_template)))
   end
 
-  it "should show error_template" do
-    get :show, params: { id: error_template }
+  it 'shows error_template' do
+    get :show, params: {id: error_template}
     expect(response.status).to eq(200)
   end
 
-  it "should get edit" do
-    get :edit, params: { id: error_template }
+  it 'gets edit' do
+    get :edit, params: {id: error_template}
     expect(response.status).to eq(200)
   end
 
-  it "should update error_template" do
-    patch :update, params: { id: error_template, error_template: FactoryBot.attributes_for(:error_template) }
+  it 'updates error_template' do
+    patch :update, params: {id: error_template, error_template: FactoryBot.attributes_for(:error_template)}
     expect(response).to redirect_to(error_template_path(assigns(:error_template)))
   end
 
-  it "should destroy error_template" do
-    expect { delete :destroy, params: { id: error_template } }.to change(ErrorTemplate, :count).by(-1)
+  it 'destroys error_template' do
+    expect { delete :destroy, params: {id: error_template} }.to change(ErrorTemplate, :count).by(-1)
     expect(response).to redirect_to(error_templates_path)
   end
 end
diff --git a/spec/controllers/events_controller_spec.rb b/spec/controllers/events_controller_spec.rb
index b414a860..e59922cd 100644
--- a/spec/controllers/events_controller_spec.rb
+++ b/spec/controllers/events_controller_spec.rb
@@ -1,14 +1,18 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe EventsController do
   let(:user) { FactoryBot.create(:admin) }
-  let(:exercise) {FactoryBot.create(:fibonacci)}
-  before(:each) { allow(controller).to receive(:current_user).and_return(user) }
+  let(:exercise) { FactoryBot.create(:fibonacci) }
+
+  before { allow(controller).to receive(:current_user).and_return(user) }
 
   describe 'POST #create' do
     context 'with a valid event' do
-      let(:perform_request) { proc { post :create, params: { event: {category: 'foo', data: 'bar', exercise_id: exercise.id, file_id: exercise.files[0].id} } } }
-      before(:each) { perform_request.call }
+      let(:perform_request) { proc { post :create, params: {event: {category: 'foo', data: 'bar', exercise_id: exercise.id, file_id: exercise.files[0].id}} } }
+
+      before { perform_request.call }
 
       expect_assigns(event: Event)
 
@@ -20,13 +24,15 @@ describe EventsController do
     end
 
     context 'with an invalid event' do
-      before(:each) { post :create, params: { event: {exercise_id: 847482} } }
+      before { post :create, params: {event: {exercise_id: 847_482}} }
+
       expect_assigns(event: Event)
       expect_status(422)
     end
 
     context 'with no event' do
-      before(:each) { post :create }
+      before { post :create }
+
       expect_status(422)
     end
   end
diff --git a/spec/controllers/execution_environments_controller_spec.rb b/spec/controllers/execution_environments_controller_spec.rb
index 60f738d8..6dc8a95f 100644
--- a/spec/controllers/execution_environments_controller_spec.rb
+++ b/spec/controllers/execution_environments_controller_spec.rb
@@ -1,16 +1,20 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe ExecutionEnvironmentsController do
   let(:execution_environment) { FactoryBot.create(:ruby) }
   let(:user) { FactoryBot.create(:admin) }
-  before(:each) { allow(controller).to receive(:current_user).and_return(user) }
+
+  before { allow(controller).to receive(:current_user).and_return(user) }
 
   describe 'POST #create' do
-    before(:each) { expect(DockerClient).to receive(:image_tags).at_least(:once).and_return([]) }
+    before { expect(DockerClient).to receive(:image_tags).at_least(:once).and_return([]) }
 
     context 'with a valid execution environment' do
-      let(:perform_request) { proc { post :create, params: { execution_environment: FactoryBot.build(:ruby).attributes } } }
-      before(:each) { perform_request.call }
+      let(:perform_request) { proc { post :create, params: {execution_environment: FactoryBot.build(:ruby).attributes} } }
+
+      before { perform_request.call }
 
       expect_assigns(docker_images: Array)
       expect_assigns(execution_environment: ExecutionEnvironment)
@@ -23,7 +27,7 @@ describe ExecutionEnvironmentsController do
     end
 
     context 'with an invalid execution environment' do
-      before(:each) { post :create, params: { execution_environment: {} } }
+      before { post :create, params: {execution_environment: {}} }
 
       expect_assigns(execution_environment: ExecutionEnvironment)
       expect_status(200)
@@ -32,22 +36,22 @@ describe ExecutionEnvironmentsController do
   end
 
   describe 'DELETE #destroy' do
-    before(:each) { delete :destroy, params: { id: execution_environment.id } }
+    before { delete :destroy, params: {id: execution_environment.id} }
 
     expect_assigns(execution_environment: :execution_environment)
 
     it 'destroys the execution environment' do
       execution_environment = FactoryBot.create(:ruby)
-      expect { delete :destroy, params: { id: execution_environment.id } }.to change(ExecutionEnvironment, :count).by(-1)
+      expect { delete :destroy, params: {id: execution_environment.id} }.to change(ExecutionEnvironment, :count).by(-1)
     end
 
     expect_redirect(:execution_environments)
   end
 
   describe 'GET #edit' do
-    before(:each) do
+    before do
       expect(DockerClient).to receive(:image_tags).at_least(:once).and_return([])
-      get :edit, params: { id: execution_environment.id }
+      get :edit, params: {id: execution_environment.id}
     end
 
     expect_assigns(docker_images: Array)
@@ -59,10 +63,10 @@ describe ExecutionEnvironmentsController do
   describe 'POST #execute_command' do
     let(:command) { 'which ruby' }
 
-    before(:each) do
+    before do
       expect(DockerClient).to receive(:new).with(execution_environment: execution_environment).and_call_original
       expect_any_instance_of(DockerClient).to receive(:execute_arbitrary_command).with(command)
-      post :execute_command, params: { command: command, id: execution_environment.id }
+      post :execute_command, params: {command: command, id: execution_environment.id}
     end
 
     expect_assigns(docker_client: DockerClient)
@@ -73,7 +77,8 @@ describe ExecutionEnvironmentsController do
 
   describe 'GET #index' do
     before(:all) { FactoryBot.create_pair(:ruby) }
-    before(:each) { get :index }
+
+    before { get :index }
 
     expect_assigns(execution_environments: ExecutionEnvironment.all)
     expect_status(200)
@@ -81,7 +86,7 @@ describe ExecutionEnvironmentsController do
   end
 
   describe 'GET #new' do
-    before(:each) do
+    before do
       expect(DockerClient).to receive(:image_tags).at_least(:once).and_return([])
       get :new
     end
@@ -96,7 +101,7 @@ describe ExecutionEnvironmentsController do
     context 'when Docker is available' do
       let(:docker_images) { [1, 2, 3] }
 
-      before(:each) do
+      before do
         expect(DockerClient).to receive(:check_availability!).at_least(:once)
         expect(DockerClient).to receive(:image_tags).and_return(docker_images)
         controller.send(:set_docker_images)
@@ -108,7 +113,7 @@ describe ExecutionEnvironmentsController do
     context 'when Docker is unavailable' do
       let(:error_message) { 'Docker is unavailable' }
 
-      before(:each) do
+      before do
         expect(DockerClient).to receive(:check_availability!).at_least(:once).and_raise(DockerClient::Error.new(error_message))
         controller.send(:set_docker_images)
       end
@@ -123,7 +128,7 @@ describe ExecutionEnvironmentsController do
   end
 
   describe 'GET #shell' do
-    before(:each) { get :shell, params: { id: execution_environment.id } }
+    before { get :shell, params: {id: execution_environment.id} }
 
     expect_assigns(execution_environment: :execution_environment)
     expect_status(200)
@@ -131,7 +136,7 @@ describe ExecutionEnvironmentsController do
   end
 
   describe 'GET #statistics' do
-    before(:each) { get :statistics, params: { id: execution_environment.id } }
+    before { get :statistics, params: {id: execution_environment.id} }
 
     expect_assigns(execution_environment: :execution_environment)
     expect_status(200)
@@ -139,7 +144,7 @@ describe ExecutionEnvironmentsController do
   end
 
   describe 'GET #show' do
-    before(:each) { get :show, params: { id: execution_environment.id } }
+    before { get :show, params: {id: execution_environment.id} }
 
     expect_assigns(execution_environment: :execution_environment)
     expect_status(200)
@@ -148,9 +153,9 @@ describe ExecutionEnvironmentsController do
 
   describe 'PUT #update' do
     context 'with a valid execution environment' do
-      before(:each) do
+      before do
         expect(DockerClient).to receive(:image_tags).at_least(:once).and_return([])
-        put :update, params: { execution_environment: FactoryBot.attributes_for(:ruby), id: execution_environment.id }
+        put :update, params: {execution_environment: FactoryBot.attributes_for(:ruby), id: execution_environment.id}
       end
 
       expect_assigns(docker_images: Array)
@@ -159,7 +164,7 @@ describe ExecutionEnvironmentsController do
     end
 
     context 'with an invalid execution environment' do
-      before(:each) { put :update, params: { execution_environment: {name: ''}, id: execution_environment.id } }
+      before { put :update, params: {execution_environment: {name: ''}, id: execution_environment.id} }
 
       expect_assigns(execution_environment: ExecutionEnvironment)
       expect_status(200)
diff --git a/spec/controllers/exercises_controller_spec.rb b/spec/controllers/exercises_controller_spec.rb
index afb620aa..fc30eb21 100644
--- a/spec/controllers/exercises_controller_spec.rb
+++ b/spec/controllers/exercises_controller_spec.rb
@@ -5,12 +5,14 @@ require 'rails_helper'
 describe ExercisesController do
   let(:exercise) { FactoryBot.create(:dummy) }
   let(:user) { FactoryBot.create(:admin) }
-  before(:each) { allow(controller).to receive(:current_user).and_return(user) }
+
+  before { allow(controller).to receive(:current_user).and_return(user) }
 
   describe 'PUT #batch_update' do
-    let(:attributes) { { 'public': 'true'} }
-    let(:perform_request) { proc { put :batch_update, params: { exercises: {0 => attributes.merge(id: exercise.id)} } } }
-    before(:each) { perform_request.call }
+    let(:attributes) { {public: 'true'} }
+    let(:perform_request) { proc { put :batch_update, params: {exercises: {0 => attributes.merge(id: exercise.id)}} } }
+
+    before { perform_request.call }
 
     it 'updates the exercises' do
       expect_any_instance_of(Exercise).to receive(:update).with(attributes)
@@ -22,10 +24,10 @@ describe ExercisesController do
   end
 
   describe 'POST #clone' do
-    let(:perform_request) { proc { post :clone, params: { id: exercise.id } } }
+    let(:perform_request) { proc { post :clone, params: {id: exercise.id} } }
 
     context 'when saving succeeds' do
-      before(:each) { perform_request.call }
+      before { perform_request.call }
 
       expect_assigns(exercise: Exercise)
 
@@ -42,7 +44,7 @@ describe ExercisesController do
     end
 
     context 'when saving fails' do
-      before(:each) do
+      before do
         expect_any_instance_of(Exercise).to receive(:save).and_return(false)
         perform_request.call
       end
@@ -57,8 +59,9 @@ describe ExercisesController do
     let(:exercise_attributes) { FactoryBot.build(:dummy).attributes }
 
     context 'with a valid exercise' do
-      let(:perform_request) { proc { post :create, params: { exercise: exercise_attributes } } }
-      before(:each) { perform_request.call }
+      let(:perform_request) { proc { post :create, params: {exercise: exercise_attributes} } }
+
+      before { perform_request.call }
 
       expect_assigns(exercise: Exercise)
 
@@ -70,7 +73,7 @@ describe ExercisesController do
     end
 
     context 'when including a file' do
-      let(:perform_request) { proc { post :create, params: { exercise: exercise_attributes.merge(files_attributes: files_attributes) } } }
+      let(:perform_request) { proc { post :create, params: {exercise: exercise_attributes.merge(files_attributes: files_attributes)} } }
 
       context 'when specifying the file content within the form' do
         let(:files_attributes) { {'0' => FactoryBot.build(:file).attributes} }
@@ -116,7 +119,7 @@ describe ExercisesController do
     end
 
     context 'with an invalid exercise' do
-      before(:each) { post :create, params: { exercise: { } } }
+      before { post :create, params: {exercise: {}} }
 
       expect_assigns(exercise: Exercise)
       expect_status(200)
@@ -125,20 +128,20 @@ describe ExercisesController do
   end
 
   describe 'DELETE #destroy' do
-    before(:each) { delete :destroy, params: { id: exercise.id } }
+    before { delete :destroy, params: {id: exercise.id} }
 
     expect_assigns(exercise: :exercise)
 
     it 'destroys the exercise' do
       exercise = FactoryBot.create(:dummy)
-      expect { delete :destroy, params: { id: exercise.id } }.to change(Exercise, :count).by(-1)
+      expect { delete :destroy, params: {id: exercise.id} }.to change(Exercise, :count).by(-1)
     end
 
     expect_redirect(:exercises)
   end
 
   describe 'GET #edit' do
-    before(:each) { get :edit, params: { id: exercise.id } }
+    before { get :edit, params: {id: exercise.id} }
 
     expect_assigns(exercise: :exercise)
     expect_status(200)
@@ -146,11 +149,12 @@ describe ExercisesController do
   end
 
   describe 'GET #implement' do
-    let(:perform_request) { proc { get :implement, params: { id: exercise.id } } }
+    let(:perform_request) { proc { get :implement, params: {id: exercise.id} } }
 
     context 'with an exercise with visible files' do
       let(:exercise) { FactoryBot.create(:fibonacci) }
-      before(:each) { perform_request.call }
+
+      before { perform_request.call }
 
       expect_assigns(exercise: :exercise)
 
@@ -174,7 +178,7 @@ describe ExercisesController do
     end
 
     context 'with an exercise without visible files' do
-      before(:each) { perform_request.call }
+      before { perform_request.call }
 
       expect_assigns(exercise: :exercise)
       expect_flash_message(:alert, :'exercises.implement.no_files')
@@ -184,8 +188,10 @@ describe ExercisesController do
 
   describe 'GET #index' do
     let(:scope) { Pundit.policy_scope!(user, Exercise) }
+
     before(:all) { FactoryBot.create_pair(:dummy) }
-    before(:each) { get :index }
+
+    before { get :index }
 
     expect_assigns(exercises: :scope)
     expect_status(200)
@@ -193,7 +199,7 @@ describe ExercisesController do
   end
 
   describe 'GET #new' do
-    before(:each) { get :new }
+    before { get :new }
 
     expect_assigns(execution_environments: ExecutionEnvironment.all, exercise: Exercise)
     expect_assigns(exercise: Exercise)
@@ -203,7 +209,7 @@ describe ExercisesController do
 
   describe 'GET #show' do
     context 'as admin' do
-      before(:each) { get :show, params: { id: exercise.id } }
+      before { get :show, params: {id: exercise.id} }
 
       expect_assigns(exercise: :exercise)
       expect_status(200)
@@ -213,7 +219,7 @@ describe ExercisesController do
 
   describe 'GET #reload' do
     context 'as anyone' do
-      before(:each) { get :reload, format: :json, params: { id: exercise.id } }
+      before { get :reload, format: :json, params: {id: exercise.id} }
 
       expect_assigns(exercise: :exercise)
       expect_status(200)
@@ -222,7 +228,7 @@ describe ExercisesController do
   end
 
   describe 'GET #statistics' do
-    before(:each) { get :statistics, params: { id: exercise.id } }
+    before { get :statistics, params: {id: exercise.id} }
 
     expect_assigns(exercise: :exercise)
     expect_status(200)
@@ -231,23 +237,23 @@ describe ExercisesController do
 
   describe 'POST #submit' do
     let(:output) { {} }
-    let(:perform_request) { post :submit, format: :json, params: { id: exercise.id, submission: {cause: 'submit', exercise_id: exercise.id} } }
+    let(:perform_request) { post :submit, format: :json, params: {id: exercise.id, submission: {cause: 'submit', exercise_id: exercise.id}} }
     let(:user) { FactoryBot.create(:external_user) }
     let!(:lti_parameter) { FactoryBot.create(:lti_parameter, external_user: user, exercise: exercise) }
 
-    before(:each) do
+    before do
       allow_any_instance_of(Submission).to receive(:normalized_score).and_return(1)
       expect(controller).to receive(:collect_test_results).and_return([{score: 1, weight: 1}])
       expect(controller).to receive(:score_submission).and_call_original
     end
 
     context 'when LTI outcomes are supported' do
-      before(:each) do
+      before do
         expect(controller).to receive(:lti_outcome_service?).and_return(true)
       end
 
       context 'when the score transmission succeeds' do
-        before(:each) do
+        before do
           expect(controller).to receive(:send_score).and_return(status: 'success')
           perform_request
         end
@@ -263,7 +269,7 @@ describe ExercisesController do
       end
 
       context 'when the score transmission fails' do
-        before(:each) do
+        before do
           expect(controller).to receive(:send_score).and_return(status: 'unsupported')
           perform_request
         end
@@ -280,7 +286,7 @@ describe ExercisesController do
     end
 
     context 'when LTI outcomes are not supported' do
-      before(:each) do
+      before do
         expect(controller).to receive(:lti_outcome_service?).and_return(false)
         expect(controller).not_to receive(:send_score)
         perform_request
@@ -300,14 +306,15 @@ describe ExercisesController do
   describe 'PUT #update' do
     context 'with a valid exercise' do
       let(:exercise_attributes) { FactoryBot.build(:dummy).attributes }
-      before(:each) { put :update, params: { exercise: exercise_attributes, id: exercise.id } }
+
+      before { put :update, params: {exercise: exercise_attributes, id: exercise.id} }
 
       expect_assigns(exercise: Exercise)
       expect_redirect(:exercise)
     end
 
     context 'with an invalid exercise' do
-      before(:each) { put :update, params: { exercise: {title: ''}, id: exercise.id } }
+      before { put :update, params: {exercise: {title: ''}, id: exercise.id} }
 
       expect_assigns(exercise: Exercise)
       expect_status(200)
@@ -321,7 +328,7 @@ describe ExercisesController do
   describe 'POST #export_external_check' do
     render_views
 
-    let(:post_request) { post :export_external_check, params: { id: exercise.id } }
+    let(:post_request) { post :export_external_check, params: {id: exercise.id} }
     let!(:codeharbor_link) { FactoryBot.create(:codeharbor_link, user: user) }
     let(:external_check_hash) { {message: message, exercise_found: true, update_right: update_right, error: error} }
     let(:message) { 'message' }
@@ -509,7 +516,7 @@ describe ExercisesController do
     end
 
     context 'when the imported exercise is invalid' do
-      before { allow(ProformaService::Import).to receive(:call) { imported_exercise.tap { |e| e.files = [] }.tap { |e| e.title = nil } } }
+      before { allow(ProformaService::Import).to receive(:call) { imported_exercise.tap {|e| e.files = [] }.tap {|e| e.title = nil } } }
 
       it 'responds with correct status code' do
         expect { post_request }.not_to(change { imported_exercise.reload.files.count })
diff --git a/spec/controllers/external_users_controller_spec.rb b/spec/controllers/external_users_controller_spec.rb
index 20699899..40286549 100644
--- a/spec/controllers/external_users_controller_spec.rb
+++ b/spec/controllers/external_users_controller_spec.rb
@@ -1,12 +1,15 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe ExternalUsersController do
   let(:user) { FactoryBot.build(:admin) }
   let!(:users) { FactoryBot.create_pair(:external_user) }
-  before(:each) { allow(controller).to receive(:current_user).and_return(user) }
+
+  before { allow(controller).to receive(:current_user).and_return(user) }
 
   describe 'GET #index' do
-    before(:each) { get :index }
+    before { get :index }
 
     expect_assigns(users: ExternalUser.all)
     expect_status(200)
@@ -14,7 +17,7 @@ describe ExternalUsersController do
   end
 
   describe 'GET #show' do
-    before(:each) { get :show, params: { id: users.first.id } }
+    before { get :show, params: {id: users.first.id} }
 
     expect_assigns(user: ExternalUser)
     expect_status(200)
diff --git a/spec/controllers/file_types_controller_spec.rb b/spec/controllers/file_types_controller_spec.rb
index 1041d703..783b3599 100644
--- a/spec/controllers/file_types_controller_spec.rb
+++ b/spec/controllers/file_types_controller_spec.rb
@@ -1,14 +1,18 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe FileTypesController do
   let(:file_type) { FactoryBot.create(:dot_rb) }
   let(:user) { FactoryBot.create(:admin) }
-  before(:each) { allow(controller).to receive(:current_user).and_return(user) }
+
+  before { allow(controller).to receive(:current_user).and_return(user) }
 
   describe 'POST #create' do
     context 'with a valid file type' do
-      let(:perform_request) { proc { post :create, params: { file_type: FactoryBot.attributes_for(:dot_rb) } } }
-      before(:each) { perform_request.call }
+      let(:perform_request) { proc { post :create, params: {file_type: FactoryBot.attributes_for(:dot_rb)} } }
+
+      before { perform_request.call }
 
       expect_assigns(editor_modes: Array)
       expect_assigns(file_type: FileType)
@@ -21,7 +25,7 @@ describe FileTypesController do
     end
 
     context 'with an invalid file type' do
-      before(:each) { post :create, params: { file_type: {  } } }
+      before { post :create, params: {file_type: {}} }
 
       expect_assigns(editor_modes: Array)
       expect_assigns(file_type: FileType)
@@ -31,20 +35,20 @@ describe FileTypesController do
   end
 
   describe 'DELETE #destroy' do
-    before(:each) { delete :destroy, params: { id: file_type.id } }
+    before { delete :destroy, params: {id: file_type.id} }
 
     expect_assigns(file_type: FileType)
 
     it 'destroys the file type' do
       file_type = FactoryBot.create(:dot_rb)
-      expect { delete :destroy, params: { id: file_type.id } }.to change(FileType, :count).by(-1)
+      expect { delete :destroy, params: {id: file_type.id} }.to change(FileType, :count).by(-1)
     end
 
     expect_redirect(:file_types)
   end
 
   describe 'GET #edit' do
-    before(:each) { get :edit, params: { id: file_type.id } }
+    before { get :edit, params: {id: file_type.id} }
 
     expect_assigns(editor_modes: Array)
     expect_assigns(file_type: FileType)
@@ -54,7 +58,8 @@ describe FileTypesController do
 
   describe 'GET #index' do
     before(:all) { FactoryBot.create_pair(:dot_rb) }
-    before(:each) { get :index }
+
+    before { get :index }
 
     expect_assigns(file_types: FileType.all)
     expect_status(200)
@@ -62,7 +67,7 @@ describe FileTypesController do
   end
 
   describe 'GET #new' do
-    before(:each) { get :new }
+    before { get :new }
 
     expect_assigns(editor_modes: Array)
     expect_assigns(file_type: FileType)
@@ -71,7 +76,7 @@ describe FileTypesController do
   end
 
   describe 'GET #show' do
-    before(:each) { get :show, params: { id: file_type.id } }
+    before { get :show, params: {id: file_type.id} }
 
     expect_assigns(file_type: :file_type)
     expect_status(200)
@@ -80,7 +85,7 @@ describe FileTypesController do
 
   describe 'PUT #update' do
     context 'with a valid file type' do
-      before(:each) { put :update, params: { file_type: FactoryBot.attributes_for(:dot_rb), id: file_type.id } }
+      before { put :update, params: {file_type: FactoryBot.attributes_for(:dot_rb), id: file_type.id} }
 
       expect_assigns(editor_modes: Array)
       expect_assigns(file_type: FileType)
@@ -88,7 +93,7 @@ describe FileTypesController do
     end
 
     context 'with an invalid file type' do
-      before(:each) { put :update, params: { file_type: {name: ''}, id: file_type.id } }
+      before { put :update, params: {file_type: {name: ''}, id: file_type.id} }
 
       expect_assigns(editor_modes: Array)
       expect_assigns(file_type: FileType)
diff --git a/spec/controllers/internal_users_controller_spec.rb b/spec/controllers/internal_users_controller_spec.rb
index d354edde..5b12e492 100644
--- a/spec/controllers/internal_users_controller_spec.rb
+++ b/spec/controllers/internal_users_controller_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe InternalUsersController do
@@ -7,28 +9,28 @@ describe InternalUsersController do
   describe 'GET #activate' do
     let(:user) { InternalUser.create(FactoryBot.attributes_for(:teacher)) }
 
-    before(:each) do
+    before do
       user.send(:setup_activation)
       user.save(validate: false)
     end
 
     context 'without a valid activation token' do
-      before(:each) { get :activate, params: { id: user.id } }
+      before { get :activate, params: {id: user.id} }
 
       expect_redirect(:root)
     end
 
     context 'with an already activated user' do
-      before(:each) do
+      before do
         user.activate!
-        get :activate, params: { id: user.id, token: user.activation_token }
+        get :activate, params: {id: user.id, token: user.activation_token}
       end
 
       expect_redirect(:root)
     end
 
     context 'with valid preconditions' do
-      before(:each) { get :activate, params: { id: user.id, token: user.activation_token } }
+      before { get :activate, params: {id: user.id, token: user.activation_token} }
 
       expect_assigns(user: InternalUser)
       expect_status(200)
@@ -40,29 +42,29 @@ describe InternalUsersController do
     let(:user) { InternalUser.create(FactoryBot.build(:teacher).attributes) }
     let(:password) { SecureRandom.hex }
 
-    before(:each) do
+    before do
       user.send(:setup_activation)
       user.save(validate: false)
       expect(user.activation_token).to be_present
     end
 
     context 'without a valid activation token' do
-      before(:each) { put :activate, params: { id: user.id } }
+      before { put :activate, params: {id: user.id} }
 
       expect_redirect(:root)
     end
 
     context 'with an already activated user' do
-      before(:each) do
+      before do
         user.activate!
-        put :activate, params: { id: user.id, internal_user: {activation_token: user.activation_token, password: password, password_confirmation: password} }
+        put :activate, params: {id: user.id, internal_user: {activation_token: user.activation_token, password: password, password_confirmation: password}}
       end
 
       expect_redirect(:root)
     end
 
     context 'without a password' do
-      before(:each) { put :activate, params: { id: user.id, internal_user: {activation_token: user.activation_token} } }
+      before { put :activate, params: {id: user.id, internal_user: {activation_token: user.activation_token}} }
 
       expect_assigns(user: InternalUser)
 
@@ -74,7 +76,7 @@ describe InternalUsersController do
     end
 
     context 'without a valid password confirmation' do
-      before(:each) { put :activate, params: { id: user.id, internal_user: {activation_token: user.activation_token, password: password, password_confirmation: ''} } }
+      before { put :activate, params: {id: user.id, internal_user: {activation_token: user.activation_token, password: password, password_confirmation: ''}} }
 
       expect_assigns(user: InternalUser)
 
@@ -86,7 +88,7 @@ describe InternalUsersController do
     end
 
     context 'with valid preconditions' do
-      before(:each) { put :activate, params: { id: user.id, internal_user: {activation_token: user.activation_token, password: password, password_confirmation: password} } }
+      before { put :activate, params: {id: user.id, internal_user: {activation_token: user.activation_token, password: password, password_confirmation: password}} }
 
       expect_assigns(user: InternalUser)
 
@@ -100,11 +102,12 @@ describe InternalUsersController do
   end
 
   describe 'POST #create' do
-    before(:each) { allow(controller).to receive(:current_user).and_return(user) }
+    before { allow(controller).to receive(:current_user).and_return(user) }
 
     context 'with a valid internal user' do
-      let(:perform_request) { proc { post :create, params: { internal_user: FactoryBot.build(:teacher).attributes } } }
-      before(:each) { perform_request.call }
+      let(:perform_request) { proc { post :create, params: {internal_user: FactoryBot.build(:teacher).attributes} } }
+
+      before { perform_request.call }
 
       expect_assigns(user: InternalUser)
 
@@ -129,7 +132,7 @@ describe InternalUsersController do
     end
 
     context 'with an invalid internal user' do
-      before(:each) { post :create, params: { internal_user: {} } }
+      before { post :create, params: {internal_user: {}} }
 
       expect_assigns(user: InternalUser)
       expect_status(200)
@@ -138,24 +141,24 @@ describe InternalUsersController do
   end
 
   describe 'DELETE #destroy' do
-    before(:each) do
+    before do
       allow(controller).to receive(:current_user).and_return(user)
-      delete :destroy, params: { id: users.first.id }
+      delete :destroy, params: {id: users.first.id}
     end
 
     expect_assigns(user: InternalUser)
 
     it 'destroys the internal user' do
-      expect { delete :destroy, params: { id: InternalUser.last.id } }.to change(InternalUser, :count).by(-1)
+      expect { delete :destroy, params: {id: InternalUser.last.id} }.to change(InternalUser, :count).by(-1)
     end
 
     expect_redirect(:internal_users)
   end
 
   describe 'GET #edit' do
-    before(:each) do
+    before do
       allow(controller).to receive(:current_user).and_return(user)
-      get :edit, params: { id: users.first.id }
+      get :edit, params: {id: users.first.id}
     end
 
     expect_assigns(user: InternalUser)
@@ -165,7 +168,7 @@ describe InternalUsersController do
 
   describe 'GET #forgot_password' do
     context 'when no user is logged in' do
-      before(:each) do
+      before do
         allow(controller).to receive(:set_sentry_context).and_return(nil)
 
         expect(controller).to receive(:current_user).and_return(nil)
@@ -177,7 +180,7 @@ describe InternalUsersController do
     end
 
     context 'when a user is already logged in' do
-      before(:each) do
+      before do
         allow(controller).to receive(:set_sentry_context).and_return(nil)
 
         expect(controller).to receive(:current_user).and_return(user)
@@ -191,8 +194,9 @@ describe InternalUsersController do
 
   describe 'POST #forgot_password' do
     context 'with an email address' do
-      let(:perform_request) { proc { post :forgot_password, params: { email: user.email } } }
-      before(:each) { perform_request.call }
+      let(:perform_request) { proc { post :forgot_password, params: {email: user.email} } }
+
+      before { perform_request.call }
 
       it 'delivers instructions to reset the password' do
         expect(InternalUser).to receive(:where).and_return([user])
@@ -204,7 +208,7 @@ describe InternalUsersController do
     end
 
     context 'without an email address' do
-      before(:each) { post :forgot_password }
+      before { post :forgot_password }
 
       expect_status(200)
       expect_template(:forgot_password)
@@ -212,7 +216,7 @@ describe InternalUsersController do
   end
 
   describe 'GET #index' do
-    before(:each) do
+    before do
       allow(controller).to receive(:current_user).and_return(user)
       get :index
     end
@@ -223,7 +227,7 @@ describe InternalUsersController do
   end
 
   describe 'GET #new' do
-    before(:each) do
+    before do
       allow(controller).to receive(:current_user).and_return(user)
       get :new
     end
@@ -237,15 +241,15 @@ describe InternalUsersController do
     let(:user) { users.first }
 
     context 'without a valid password reset token' do
-      before(:each) { get :reset_password, params: { id: user.id } }
+      before { get :reset_password, params: {id: user.id} }
 
       expect_redirect(:root)
     end
 
     context 'with a valid password reset token' do
-      before(:each) do
+      before do
         user.deliver_reset_password_instructions!
-        get :reset_password, params: { id: user.id, token: user.reset_password_token }
+        get :reset_password, params: {id: user.id, token: user.reset_password_token}
       end
 
       expect_assigns(user: :user)
@@ -256,10 +260,11 @@ describe InternalUsersController do
 
   describe 'PUT #reset_password' do
     let(:user) { users.first }
-    before(:each) { user.deliver_reset_password_instructions! }
+
+    before { user.deliver_reset_password_instructions! }
 
     context 'without a valid password reset token' do
-      before(:each) { put :reset_password, params: { id: user.id } }
+      before { put :reset_password, params: {id: user.id} }
 
       expect_redirect(:root)
     end
@@ -268,8 +273,9 @@ describe InternalUsersController do
       let(:password) { 'foo' }
 
       context 'with a matching password confirmation' do
-        let(:perform_request) { proc { put :reset_password, params: { internal_user: {password: password, password_confirmation: password}, id: user.id, token: user.reset_password_token } } }
-        before(:each) { perform_request.call }
+        let(:perform_request) { proc { put :reset_password, params: {internal_user: {password: password, password_confirmation: password}, id: user.id, token: user.reset_password_token} } }
+
+        before { perform_request.call }
 
         expect_assigns(user: :user)
 
@@ -281,8 +287,8 @@ describe InternalUsersController do
       end
 
       context 'without a matching password confirmation' do
-        before(:each) do
-          put :reset_password, params: { internal_user: {password: password, password_confirmation: ''}, id: users.first.id, token: user.reset_password_token }
+        before do
+          put :reset_password, params: {internal_user: {password: password, password_confirmation: ''}, id: users.first.id, token: user.reset_password_token}
         end
 
         expect_assigns(user: :user)
@@ -293,9 +299,9 @@ describe InternalUsersController do
   end
 
   describe 'GET #show' do
-    before(:each) do
+    before do
       allow(controller).to receive(:current_user).and_return(user)
-      get :show, params: { id: users.first.id }
+      get :show, params: {id: users.first.id}
     end
 
     expect_assigns(user: InternalUser)
@@ -304,17 +310,17 @@ describe InternalUsersController do
   end
 
   describe 'PUT #update' do
-    before(:each) { allow(controller).to receive(:current_user).and_return(user) }
+    before { allow(controller).to receive(:current_user).and_return(user) }
 
     context 'with a valid internal user' do
-      before(:each) { put :update, params: { internal_user: FactoryBot.attributes_for(:teacher), id: users.first.id } }
+      before { put :update, params: {internal_user: FactoryBot.attributes_for(:teacher), id: users.first.id} }
 
       expect_assigns(user: InternalUser)
       expect_redirect { user }
     end
 
     context 'with an invalid internal user' do
-      before(:each) { put :update, params: { internal_user: {email: ''}, id: users.first.id } }
+      before { put :update, params: {internal_user: {email: ''}, id: users.first.id} }
 
       expect_assigns(user: InternalUser)
       expect_status(200)
diff --git a/spec/controllers/request_for_comments_controller_spec.rb b/spec/controllers/request_for_comments_controller_spec.rb
index 95bf6aec..074aa644 100644
--- a/spec/controllers/request_for_comments_controller_spec.rb
+++ b/spec/controllers/request_for_comments_controller_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe RequestForCommentsController do
@@ -24,7 +26,7 @@ describe RequestForCommentsController do
       rfc_other_study_group.user.update(study_groups: [another_study_group])
       rfc_other_study_group.submission.update(study_group: another_study_group)
 
-      get :index, params: { "q[submission_study_group_id_in][]": my_study_group.id }
+      get :index, params: {"q[submission_study_group_id_in][]": my_study_group.id}
 
       expect(assigns(:request_for_comments)).to eq([rfc_within_my_study_group])
     end
@@ -47,7 +49,7 @@ describe RequestForCommentsController do
   describe 'GET #get_rfcs_for_exercise' do
     before do
       exercise = FactoryBot.create(:even_odd)
-      get :get_rfcs_for_exercise, params: { exercise_id: exercise.id }
+      get :get_rfcs_for_exercise, params: {exercise_id: exercise.id}
     end
 
     expect_status(200)
diff --git a/spec/controllers/sessions_controller_spec.rb b/spec/controllers/sessions_controller_spec.rb
index 043a7912..9d882c4a 100644
--- a/spec/controllers/sessions_controller_spec.rb
+++ b/spec/controllers/sessions_controller_spec.rb
@@ -11,9 +11,9 @@ describe SessionsController do
     let(:user_attributes) { FactoryBot.build(:teacher).attributes }
 
     context 'with valid credentials' do
-      before(:each) do
+      before do
         user.activate!
-        post :create, params: { email: user.email, password: password, remember_me: 1 }
+        post :create, params: {email: user.email, password: password, remember_me: 1}
       end
 
       expect_flash_message(:notice, :'sessions.create.success')
@@ -21,7 +21,7 @@ describe SessionsController do
     end
 
     context 'with invalid credentials' do
-      before(:each) { post :create, params: { email: user.email, password: '', remember_me: 1 } }
+      before { post :create, params: {email: user.email, password: '', remember_me: 1} }
 
       expect_flash_message(:danger, :'sessions.create.failure')
       expect_template(:new)
@@ -32,7 +32,8 @@ describe SessionsController do
     let(:exercise) { FactoryBot.create(:dummy) }
     let(:exercise2) { FactoryBot.create(:dummy) }
     let(:nonce) { SecureRandom.hex }
-    before(:each) { I18n.locale = I18n.default_locale }
+
+    before { I18n.locale = I18n.default_locale }
 
     context 'without OAuth parameters' do
       it 'refuses the LTI launch' do
@@ -44,14 +45,14 @@ describe SessionsController do
     context 'without a valid consumer key' do
       it 'refuses the LTI launch' do
         expect(controller).to receive(:refuse_lti_launch).with(message: I18n.t('sessions.oauth.invalid_consumer')).and_call_original
-        post :create_through_lti, params: { oauth_consumer_key: SecureRandom.hex, oauth_signature: SecureRandom.hex }
+        post :create_through_lti, params: {oauth_consumer_key: SecureRandom.hex, oauth_signature: SecureRandom.hex}
       end
     end
 
     context 'with an invalid OAuth signature' do
       it 'refuses the LTI launch' do
         expect(controller).to receive(:refuse_lti_launch).with(message: I18n.t('sessions.oauth.invalid_signature')).and_call_original
-        post :create_through_lti, params: { oauth_consumer_key: consumer.oauth_key, oauth_signature: SecureRandom.hex }
+        post :create_through_lti, params: {oauth_consumer_key: consumer.oauth_key, oauth_signature: SecureRandom.hex}
       end
     end
 
@@ -60,7 +61,7 @@ describe SessionsController do
         expect_any_instance_of(IMS::LTI::ToolProvider).to receive(:valid_request?).and_return(true)
         expect(NonceStore).to receive(:has?).with(nonce).and_return(true)
         expect(controller).to receive(:refuse_lti_launch).with(message: I18n.t('sessions.oauth.used_nonce')).and_call_original
-        post :create_through_lti, params: { oauth_consumer_key: consumer.oauth_key, oauth_nonce: nonce, oauth_signature: SecureRandom.hex }
+        post :create_through_lti, params: {oauth_consumer_key: consumer.oauth_key, oauth_nonce: nonce, oauth_signature: SecureRandom.hex}
       end
     end
 
@@ -68,15 +69,16 @@ describe SessionsController do
       it 'refuses the LTI launch' do
         expect_any_instance_of(IMS::LTI::ToolProvider).to receive(:valid_request?).and_return(true)
         expect(controller).to receive(:refuse_lti_launch).with(message: I18n.t('sessions.oauth.invalid_exercise_token')).and_call_original
-        post :create_through_lti, params: { custom_token: '', oauth_consumer_key: consumer.oauth_key, oauth_nonce: nonce, oauth_signature: SecureRandom.hex, user_id: '123' }
+        post :create_through_lti, params: {custom_token: '', oauth_consumer_key: consumer.oauth_key, oauth_nonce: nonce, oauth_signature: SecureRandom.hex, user_id: '123'}
       end
     end
 
     context 'with valid launch parameters' do
       let(:locale) { :de }
-      let(:perform_request) { post :create_through_lti, params: { custom_locale: locale, custom_token: exercise.token, oauth_consumer_key: consumer.oauth_key, oauth_nonce: nonce, oauth_signature: SecureRandom.hex, user_id: user.external_id } }
+      let(:perform_request) { post :create_through_lti, params: {custom_locale: locale, custom_token: exercise.token, oauth_consumer_key: consumer.oauth_key, oauth_nonce: nonce, oauth_signature: SecureRandom.hex, user_id: user.external_id} }
       let(:user) { FactoryBot.create(:external_user, consumer_id: consumer.id) }
-      before(:each) { expect_any_instance_of(IMS::LTI::ToolProvider).to receive(:valid_request?).and_return(true) }
+
+      before { expect_any_instance_of(IMS::LTI::ToolProvider).to receive(:valid_request?).and_return(true) }
 
       it 'assigns the current user' do
         perform_request
@@ -96,7 +98,7 @@ describe SessionsController do
       end
 
       it 'stores LTI parameters in the session' do
-        #Todo replace session with lti_parameter /should be done already
+        # Todo replace session with lti_parameter /should be done already
         expect(controller).to receive(:store_lti_session_data)
         perform_request
       end
@@ -109,7 +111,7 @@ describe SessionsController do
       context 'when LTI outcomes are supported' do
         let(:message) { I18n.t('sessions.create_through_lti.session_with_outcome', consumer: consumer) }
 
-        before(:each) do
+        before do
           expect(controller).to receive(:lti_outcome_service?).and_return(true)
           perform_request
         end
@@ -120,7 +122,7 @@ describe SessionsController do
       context 'when LTI outcomes are not supported' do
         let(:message) { I18n.t('sessions.create_through_lti.session_without_outcome', consumer: consumer) }
 
-        before(:each) do
+        before do
           expect(controller).to receive(:lti_outcome_service?).and_return(false)
           perform_request
         end
@@ -135,7 +137,7 @@ describe SessionsController do
 
       it 'redirects to recommended exercise if requested token of proxy exercise' do
         FactoryBot.create(:proxy_exercise, exercises: [exercise])
-        post :create_through_lti, params: { custom_locale: locale, custom_token: ProxyExercise.first.token, oauth_consumer_key: consumer.oauth_key, oauth_nonce: nonce, oauth_signature: SecureRandom.hex, user_id: user.external_id }
+        post :create_through_lti, params: {custom_locale: locale, custom_token: ProxyExercise.first.token, oauth_consumer_key: consumer.oauth_key, oauth_nonce: nonce, oauth_signature: SecureRandom.hex, user_id: user.external_id}
         expect(controller).to redirect_to(implement_exercise_path(exercise.id))
       end
 
@@ -146,7 +148,7 @@ describe SessionsController do
         exercise.save
         exercise2.expected_difficulty = 1
         exercise2.save
-        post :create_through_lti, params: { custom_locale: locale, custom_token: ProxyExercise.first.token, oauth_consumer_key: consumer.oauth_key, oauth_nonce: nonce, oauth_signature: SecureRandom.hex, user_id: user.external_id }
+        post :create_through_lti, params: {custom_locale: locale, custom_token: ProxyExercise.first.token, oauth_consumer_key: consumer.oauth_key, oauth_nonce: nonce, oauth_signature: SecureRandom.hex, user_id: user.external_id}
         expect(controller).to redirect_to(implement_exercise_path(exercise2.id))
       end
     end
@@ -154,13 +156,14 @@ describe SessionsController do
 
   describe 'DELETE #destroy' do
     let(:user) { double }
-    before(:each) {
+
+    before do
       allow(controller).to receive(:set_sentry_context).and_return(nil)
       expect(controller).to receive(:current_user).at_least(:once).and_return(user)
-    }
+    end
 
     context 'with an internal user' do
-      before(:each) do
+      before do
         allow(user).to receive(:external_user?).and_return(false)
         allow(user).to receive(:forget_me!)
         delete :destroy
@@ -177,13 +180,13 @@ describe SessionsController do
     end
 
     context 'with an external user' do
-      before(:each) do
+      before do
         allow(user).to receive(:external_user?).and_return(true)
         delete :destroy
       end
 
       it 'clears the session' do
-        #Todo replace session with lti_parameter /should be done already
+        # Todo replace session with lti_parameter /should be done already
         expect(controller).to receive(:clear_lti_session_data)
         delete :destroy
       end
@@ -195,19 +198,11 @@ describe SessionsController do
   end
 
   describe 'GET #destroy_through_lti' do
-    let(:perform_request) { proc { get :destroy_through_lti, params: { consumer_id: consumer.id, submission_id: submission.id } } }
-    let(:submission) { FactoryBot.create(:submission, exercise: FactoryBot.create(:dummy)) }
-
-    before(:each) do
-      #Todo replace session with lti_parameter
-      #Todo create LtiParameter Object
-      # session[:lti_parameters] = {}
-    end
-
-    before(:each) { perform_request.call }
+    let(:perform_request) { proc { get :destroy_through_lti, params: {consumer_id: consumer.id, submission_id: submission.id} } }
+    let(:submission) { FactoryBot.create(:submission, exercise: FactoryBot.create(:dummy)) }    before { perform_request.call }
 
     it 'clears the session' do
-      #Todo replace session with lti_parameter /should be done already
+      # Todo replace session with lti_parameter /should be done already
       expect(controller).to receive(:clear_lti_session_data)
       perform_request.call
     end
@@ -218,7 +213,7 @@ describe SessionsController do
 
   describe 'GET #new' do
     context 'when no user is logged in' do
-      before(:each) do
+      before do
         allow(controller).to receive(:set_sentry_context).and_return(nil)
 
         expect(controller).to receive(:current_user).and_return(nil)
@@ -230,7 +225,7 @@ describe SessionsController do
     end
 
     context 'when a user is already logged in' do
-      before(:each) do
+      before do
         allow(controller).to receive(:set_sentry_context).and_return(nil)
 
         expect(controller).to receive(:current_user).and_return(FactoryBot.build(:teacher))
diff --git a/spec/controllers/statistics_controller_spec.rb b/spec/controllers/statistics_controller_spec.rb
index c193315d..8ddd30c2 100644
--- a/spec/controllers/statistics_controller_spec.rb
+++ b/spec/controllers/statistics_controller_spec.rb
@@ -1,34 +1,36 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe StatisticsController do
   let(:user) { FactoryBot.create(:admin) }
-  before(:each) { allow(controller).to receive(:current_user).and_return(user) }
 
-  [:show, :graphs].each do |route|
+  before { allow(controller).to receive(:current_user).and_return(user) }
+
+  %i[show graphs].each do |route|
     describe "GET ##{route}" do
-      before(:each) { get route }
+      before { get route }
 
       expect_status(200)
       expect_template(route)
     end
   end
 
-  [:user_activity_history, :rfc_activity_history].each do |route|
+  %i[user_activity_history rfc_activity_history].each do |route|
     describe "GET ##{route}" do
-      before(:each) { get route }
+      before { get route }
 
       expect_status(200)
       expect_template(:activity_history)
     end
   end
 
-  [:show, :user_activity, :user_activity_history, :rfc_activity, :rfc_activity_history].each do |route|
+  %i[show user_activity user_activity_history rfc_activity rfc_activity_history].each do |route|
     describe "GET ##{route}.json" do
-      before(:each) { get route, format: :json }
+      before { get route, format: :json }
 
       expect_status(200)
       expect_json
     end
   end
-
 end
diff --git a/spec/controllers/submissions_controller_spec.rb b/spec/controllers/submissions_controller_spec.rb
index 62dfdcd4..448c8bf6 100644
--- a/spec/controllers/submissions_controller_spec.rb
+++ b/spec/controllers/submissions_controller_spec.rb
@@ -1,19 +1,23 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe SubmissionsController do
   let(:submission) { FactoryBot.create(:submission) }
   let(:user) { FactoryBot.create(:admin) }
-  before(:each) { allow(controller).to receive(:current_user).and_return(user) }
+
+  before { allow(controller).to receive(:current_user).and_return(user) }
 
   describe 'POST #create' do
-    before(:each) do
+    before do
       controller.request.accept = 'application/json'
     end
 
     context 'with a valid submission' do
       let(:exercise) { FactoryBot.create(:hello_world) }
-      let(:perform_request) { proc { post :create, format: :json, params: { submission: FactoryBot.attributes_for(:submission, exercise_id: exercise.id) } } }
-      before(:each) { perform_request.call }
+      let(:perform_request) { proc { post :create, format: :json, params: {submission: FactoryBot.attributes_for(:submission, exercise_id: exercise.id)} } }
+
+      before { perform_request.call }
 
       expect_assigns(submission: Submission)
 
@@ -26,7 +30,7 @@ describe SubmissionsController do
     end
 
     context 'with an invalid submission' do
-      before(:each) { post :create, params: { submission: {  } } }
+      before { post :create, params: {submission: {}} }
 
       expect_assigns(submission: Submission)
       expect_json
@@ -36,17 +40,18 @@ describe SubmissionsController do
 
   describe 'GET #download_file' do
     context 'with an invalid filename' do
-      before(:each) { get :download_file, params: { filename: SecureRandom.hex, id: submission.id } }
+      before { get :download_file, params: {filename: SecureRandom.hex, id: submission.id} }
 
       expect_status(404)
     end
 
     context 'with a valid binary filename' do
       let(:submission) { FactoryBot.create(:submission, exercise: FactoryBot.create(:sql_select)) }
-      before(:each) { get :download_file, params: { filename: file.name_with_extension, id: submission.id } }
+
+      before { get :download_file, params: {filename: file.name_with_extension, id: submission.id} }
 
       context 'for a binary file' do
-        let(:file) { submission.collect_files.detect { |file| file.name == 'exercise' && file.file_type.file_extension == '.sql' } }
+        let(:file) { submission.collect_files.detect {|file| file.name == 'exercise' && file.file_type.file_extension == '.sql' } }
 
         expect_assigns(file: :file)
         expect_assigns(submission: :submission)
@@ -61,10 +66,11 @@ describe SubmissionsController do
 
     context 'with a valid filename' do
       let(:submission) { FactoryBot.create(:submission, exercise: FactoryBot.create(:audio_video)) }
-      before(:each) { get :download_file, params: { filename: file.name_with_extension, id: submission.id } }
+
+      before { get :download_file, params: {filename: file.name_with_extension, id: submission.id} }
 
       context 'for a binary file' do
-        let(:file) { submission.collect_files.detect { |file| file.file_type.file_extension == '.mp4' } }
+        let(:file) { submission.collect_files.detect {|file| file.file_type.file_extension == '.mp4' } }
 
         expect_assigns(file: :file)
         expect_assigns(submission: :submission)
@@ -77,7 +83,7 @@ describe SubmissionsController do
       end
 
       context 'for a non-binary file' do
-        let(:file) { submission.collect_files.detect { |file| file.file_type.file_extension == '.js' } }
+        let(:file) { submission.collect_files.detect {|file| file.file_type.file_extension == '.js' } }
 
         expect_assigns(file: :file)
         expect_assigns(submission: :submission)
@@ -93,7 +99,8 @@ describe SubmissionsController do
 
   describe 'GET #index' do
     before(:all) { FactoryBot.create_pair(:submission) }
-    before(:each) { get :index }
+
+    before { get :index }
 
     expect_assigns(submissions: Submission.all)
     expect_status(200)
@@ -104,17 +111,18 @@ describe SubmissionsController do
     let(:file) { submission.files.first }
 
     context 'with an invalid filename' do
-      before(:each) { get :render_file, params: { filename: SecureRandom.hex, id: submission.id } }
+      before { get :render_file, params: {filename: SecureRandom.hex, id: submission.id} }
 
       expect_status(404)
     end
 
     context 'with a valid filename' do
       let(:submission) { FactoryBot.create(:submission, exercise: FactoryBot.create(:audio_video)) }
-      before(:each) { get :render_file, params: { filename: file.name_with_extension, id: submission.id } }
+
+      before { get :render_file, params: {filename: file.name_with_extension, id: submission.id} }
 
       context 'for a binary file' do
-        let(:file) { submission.collect_files.detect { |file| file.file_type.file_extension == '.mp4' } }
+        let(:file) { submission.collect_files.detect {|file| file.file_type.file_extension == '.mp4' } }
 
         expect_assigns(file: :file)
         expect_assigns(submission: :submission)
@@ -127,7 +135,7 @@ describe SubmissionsController do
       end
 
       context 'for a non-binary file' do
-        let(:file) { submission.collect_files.detect { |file| file.file_type.file_extension == '.js' } }
+        let(:file) { submission.collect_files.detect {|file| file.file_type.file_extension == '.js' } }
 
         expect_assigns(file: :file)
         expect_assigns(submission: :submission)
@@ -143,24 +151,24 @@ describe SubmissionsController do
 
   describe 'GET #run' do
     let(:filename) { submission.collect_files.detect(&:main_file?).name_with_extension }
-    let(:perform_request) { get :run, params: { filename: filename , id: submission.id } }
+    let(:perform_request) { get :run, params: {filename: filename, id: submission.id} }
 
-    before(:each) do
+    before do
       expect_any_instance_of(ActionController::Live::SSE).to receive(:write).at_least(3).times
     end
 
     context 'when no errors occur during execution' do
-      before(:each) do
+      before do
         expect_any_instance_of(DockerClient).to receive(:execute_run_command).with(submission, filename).and_return({})
         perform_request
       end
 
-      pending("todo")
+      pending('todo')
     end
   end
 
   describe 'GET #show' do
-    before(:each) { get :show, params: { id: submission.id } }
+    before { get :show, params: {id: submission.id} }
 
     expect_assigns(submission: :submission)
     expect_status(200)
@@ -172,11 +180,12 @@ describe SubmissionsController do
     # https://github.com/rails/jbuilder/issues/32
     render_views
 
-    before(:each) { get :show, params: { id: submission.id }, format: :json }
+    before { get :show, params: {id: submission.id}, format: :json }
+
     expect_assigns(submission: :submission)
     expect_status(200)
 
-    [:render, :run, :test].each do |action|
+    %i[render run test].each do |action|
       describe "##{action}_url" do
         let(:url) { JSON.parse(response.body).with_indifferent_access.fetch("#{action}_url") }
 
@@ -186,45 +195,47 @@ describe SubmissionsController do
         end
 
         it 'ends with a placeholder' do
-          expect(url).to end_with(Submission::FILENAME_URL_PLACEHOLDER + '.json')
+          expect(url).to end_with("#{Submission::FILENAME_URL_PLACEHOLDER}.json")
         end
       end
     end
 
-    describe "#score_url" do
-      let(:url) { JSON.parse(response.body).with_indifferent_access.fetch("score_url") }
+    describe '#score_url' do
+      let(:url) { JSON.parse(response.body).with_indifferent_access.fetch('score_url') }
 
-      it "corresponds to the score path" do
+      it 'corresponds to the score path' do
         expect(url).to eq(Rails.application.routes.url_helpers.score_submission_path(submission, format: :json))
       end
     end
   end
 
   describe 'GET #score' do
-    let(:perform_request) { proc { get :score, params: { id: submission.id } } }
-    before(:each) { perform_request.call }
+    let(:perform_request) { proc { get :score, params: {id: submission.id} } }
 
-    pending("todo: mock puma webserver or encapsulate tubesock call (Tubesock::HijackNotAvailable)")
+    before { perform_request.call }
+
+    pending('todo: mock puma webserver or encapsulate tubesock call (Tubesock::HijackNotAvailable)')
   end
 
   describe 'GET #test' do
     let(:filename) { submission.collect_files.detect(&:teacher_defined_assessment?).name_with_extension }
     let(:output) { {} }
 
-    before(:each) do
+    before do
       expect_any_instance_of(DockerClient).to receive(:execute_test_command).with(submission, filename)
-      get :test, filename: filename, id: submission.id
+      get :test, params: {filename: filename, id: submission.id}
     end
 
-    pending("todo")
+    pending('todo')
   end
 
   describe '#with_server_sent_events' do
     let(:response) { ActionDispatch::TestResponse.new }
-    before(:each) { allow(controller).to receive(:response).and_return(response) }
+
+    before { allow(controller).to receive(:response).and_return(response) }
 
     context 'when no error occurs' do
-      after(:each) { controller.send(:with_server_sent_events) }
+      after { controller.send(:with_server_sent_events) }
 
       it 'uses server-sent events' do
         expect(ActionController::Live::SSE).to receive(:new).and_call_original
@@ -246,7 +257,7 @@ describe SubmissionsController do
     end
 
     context 'when an error occurs' do
-      after(:each) { controller.send(:with_server_sent_events) { fail } }
+      after { controller.send(:with_server_sent_events) { raise } }
 
       it 'uses server-sent events' do
         expect(ActionController::Live::SSE).to receive(:new).and_call_original
diff --git a/spec/factories/code_ocean/file.rb b/spec/factories/code_ocean/file.rb
index 61241593..3e3132ee 100644
--- a/spec/factories/code_ocean/file.rb
+++ b/spec/factories/code_ocean/file.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'seeds_helper'
 
 module CodeOcean
diff --git a/spec/factories/codeharbor_link.rb b/spec/factories/codeharbor_link.rb
index c960eb9a..1456c718 100644
--- a/spec/factories/codeharbor_link.rb
+++ b/spec/factories/codeharbor_link.rb
@@ -1,8 +1,10 @@
+# frozen_string_literal: true
+
 FactoryBot.define do
   factory :codeharbor_link do
     user { build(:teacher) }
     push_url { 'http://push.url' }
     check_uuid_url { 'http://check-uuid.url' }
-    sequence(:api_key) { |n| "api_key#{n}" }
+    sequence(:api_key) {|n| "api_key#{n}" }
   end
 end
diff --git a/spec/factories/consumer.rb b/spec/factories/consumer.rb
index 59b05b8d..06d19857 100644
--- a/spec/factories/consumer.rb
+++ b/spec/factories/consumer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 FactoryBot.define do
   factory :consumer do
     name { 'openHPI' }
diff --git a/spec/factories/error_template_attributes.rb b/spec/factories/error_template_attributes.rb
index 74d6e559..c94462a5 100644
--- a/spec/factories/error_template_attributes.rb
+++ b/spec/factories/error_template_attributes.rb
@@ -1,6 +1,8 @@
+# frozen_string_literal: true
+
 FactoryBot.define do
   factory :error_template_attribute do
-    key { "MyString" }
-    regex { "MyString" }
+    key { 'MyString' }
+    regex { 'MyString' }
   end
 end
diff --git a/spec/factories/error_templates.rb b/spec/factories/error_templates.rb
index 41286229..a0556912 100644
--- a/spec/factories/error_templates.rb
+++ b/spec/factories/error_templates.rb
@@ -1,7 +1,9 @@
+# frozen_string_literal: true
+
 FactoryBot.define do
   factory :error_template do
     association :execution_environment, factory: :ruby
-    name { "MyString" }
-    signature { "MyString" }
+    name { 'MyString' }
+    signature { 'MyString' }
   end
 end
diff --git a/spec/factories/execution_environment.rb b/spec/factories/execution_environment.rb
index 3961441a..5c3b50ef 100644
--- a/spec/factories/execution_environment.rb
+++ b/spec/factories/execution_environment.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 FactoryBot.define do
   factory :coffee_script, class: 'ExecutionEnvironment' do
     created_by_teacher
diff --git a/spec/factories/exercise.rb b/spec/factories/exercise.rb
index 20c460cc..07ed6243 100644
--- a/spec/factories/exercise.rb
+++ b/spec/factories/exercise.rb
@@ -4,13 +4,13 @@ require 'seeds_helper'
 
 def create_seed_file(exercise, path, file_attributes = {})
   file_extension = File.extname(path)
-  file_type = FactoryBot.create(file_attributes[:file_type] || :"dot_#{file_extension.gsub('.', '')}")
+  file_type = FactoryBot.create(file_attributes[:file_type] || :"dot_#{file_extension.delete('.')}")
   name = File.basename(path).gsub(file_extension, '')
   file_attributes.merge!(file_type: file_type, name: name, path: path.split('/')[1..-2].join('/'), role: file_attributes[:role] || 'regular_file')
   if file_type.binary?
-    file_attributes.merge!(native_file: File.open(SeedsHelper.seed_file_path(path), 'r'))
+    file_attributes[:native_file] = File.open(SeedsHelper.seed_file_path(path), 'r')
   else
-    file_attributes.merge!(content: SeedsHelper.read_seed_file(path))
+    file_attributes[:content] = SeedsHelper.read_seed_file(path)
   end
   exercise.add_file!(file_attributes)
 end
diff --git a/spec/factories/external_user.rb b/spec/factories/external_user.rb
index 41a9c3e8..d1439e1c 100644
--- a/spec/factories/external_user.rb
+++ b/spec/factories/external_user.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 FactoryBot.define do
   factory :external_user do
     association :consumer
diff --git a/spec/factories/file_type.rb b/spec/factories/file_type.rb
index f08e3b73..0dc823cc 100644
--- a/spec/factories/file_type.rb
+++ b/spec/factories/file_type.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 FactoryBot.define do
   factory :dot_coffee, class: 'FileType' do
     created_by_admin
diff --git a/spec/factories/lti_parameter.rb b/spec/factories/lti_parameter.rb
index 3d2620ad..6d5044e1 100644
--- a/spec/factories/lti_parameter.rb
+++ b/spec/factories/lti_parameter.rb
@@ -1,10 +1,11 @@
-FactoryBot.define do
+# frozen_string_literal: true
 
+FactoryBot.define do
   LTI_PARAMETERS = {
-      lis_result_sourcedid: "c2db0c7c-4411-4b27-a52b-ddfc3dc32065",
-      lis_outcome_service_url: "http://172.16.54.235:3000/courses/0132156a-9afb-434d-83cc-704780104105/sections/21c6c6f4-1fb6-43b4-af3c-04fdc098879e/items/999b1fe6-d4b6-47b7-a577-ea2b4b1041ec/tool_grading",
-      launch_presentation_return_url: "http://172.16.54.235:3000/courses/0132156a-9afb-434d-83cc-704780104105/sections/21c6c6f4-1fb6-43b4-af3c-04fdc098879e/items/999b1fe6-d4b6-47b7-a577-ea2b4b1041ec/tool_return"
-  }
+    lis_result_sourcedid: 'c2db0c7c-4411-4b27-a52b-ddfc3dc32065',
+      lis_outcome_service_url: 'http://172.16.54.235:3000/courses/0132156a-9afb-434d-83cc-704780104105/sections/21c6c6f4-1fb6-43b4-af3c-04fdc098879e/items/999b1fe6-d4b6-47b7-a577-ea2b4b1041ec/tool_grading',
+      launch_presentation_return_url: 'http://172.16.54.235:3000/courses/0132156a-9afb-434d-83cc-704780104105/sections/21c6c6f4-1fb6-43b4-af3c-04fdc098879e/items/999b1fe6-d4b6-47b7-a577-ea2b4b1041ec/tool_return',
+  }.freeze
 
   factory :lti_parameter do
     association :consumer
diff --git a/spec/factories/proxy_exercise.rb b/spec/factories/proxy_exercise.rb
index a100f8d6..cefe808d 100644
--- a/spec/factories/proxy_exercise.rb
+++ b/spec/factories/proxy_exercise.rb
@@ -1,8 +1,9 @@
+# frozen_string_literal: true
+
 FactoryBot.define do
   factory :proxy_exercise, class: 'ProxyExercise' do
     created_by_teacher
     token { 'dummytoken' }
     title { 'Dummy' }
   end
-
 end
diff --git a/spec/factories/shared_traits.rb b/spec/factories/shared_traits.rb
index 43847e8c..f9233cd6 100644
--- a/spec/factories/shared_traits.rb
+++ b/spec/factories/shared_traits.rb
@@ -1,12 +1,14 @@
+# frozen_string_literal: true
+
 FactoryBot.define do
-  [:admin, :external_user, :teacher].each do |factory_name|
+  %i[admin external_user teacher].each do |factory_name|
     trait :"created_by_#{factory_name}" do
       association :user, factory: factory_name
     end
   end
 
   trait :generated_email do
-    email { "#{name.underscore.gsub(' ', '.')}@example.org" }
+    email { "#{name.underscore.tr(' ', '.')}@example.org" }
   end
 
   trait :generated_user_name do
diff --git a/spec/factories/structured_error_attributes.rb b/spec/factories/structured_error_attributes.rb
index 5652f1b6..6349580d 100644
--- a/spec/factories/structured_error_attributes.rb
+++ b/spec/factories/structured_error_attributes.rb
@@ -1,7 +1,9 @@
+# frozen_string_literal: true
+
 FactoryBot.define do
   factory :structured_error_attribute do
     association :structured_error
     association :error_template_attribute
-    value { "MyString" }
+    value { 'MyString' }
   end
 end
diff --git a/spec/factories/structured_errors.rb b/spec/factories/structured_errors.rb
index 2b61e744..921e8ff6 100644
--- a/spec/factories/structured_errors.rb
+++ b/spec/factories/structured_errors.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 FactoryBot.define do
   factory :structured_error do
     association :error_template
diff --git a/spec/factories/study_group.rb b/spec/factories/study_group.rb
index 6256adde..be4ad0ae 100644
--- a/spec/factories/study_group.rb
+++ b/spec/factories/study_group.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 FactoryBot.define do
   factory :study_group, class: 'StudyGroup' do
     association :consumer
diff --git a/spec/factories/submission.rb b/spec/factories/submission.rb
index 81cc33a9..39f9f338 100644
--- a/spec/factories/submission.rb
+++ b/spec/factories/submission.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 FactoryBot.define do
   factory :submission do
     cause { 'save' }
diff --git a/spec/factories/user_exercise_feedback.rb b/spec/factories/user_exercise_feedback.rb
index ff0ff763..9c8de052 100644
--- a/spec/factories/user_exercise_feedback.rb
+++ b/spec/factories/user_exercise_feedback.rb
@@ -1,8 +1,9 @@
+# frozen_string_literal: true
+
 FactoryBot.define do
   factory :user_exercise_feedback, class: 'UserExerciseFeedback' do
     created_by_external_user
     feedback_text { 'Most suitable exercise ever' }
     association :exercise, factory: :math
   end
-
 end
diff --git a/spec/features/authentication_spec.rb b/spec/features/authentication_spec.rb
index 31fd39fe..39704038 100644
--- a/spec/features/authentication_spec.rb
+++ b/spec/features/authentication_spec.rb
@@ -7,7 +7,7 @@ describe 'Authentication' do
   let(:password) { FactoryBot.attributes_for(:admin)[:password] }
 
   context 'when signed out' do
-    before(:each) { visit(root_path) }
+    before { visit(root_path) }
 
     it 'displays a sign in link' do
       expect(page).to have_content(I18n.t('sessions.new.link'))
@@ -35,7 +35,7 @@ describe 'Authentication' do
   end
 
   context 'when signed in' do
-    before(:each) do
+    before do
       sign_in(user, password)
       visit(root_path)
     end
diff --git a/spec/features/authorization_spec.rb b/spec/features/authorization_spec.rb
index 97d7056d..4fedf09e 100644
--- a/spec/features/authorization_spec.rb
+++ b/spec/features/authorization_spec.rb
@@ -5,7 +5,8 @@ require 'rails_helper'
 describe 'Authorization' do
   context 'as an admin' do
     let(:user) { FactoryBot.create(:admin) }
-    before(:each) { allow_any_instance_of(ApplicationController).to receive(:current_user).and_return(user) }
+
+    before { allow_any_instance_of(ApplicationController).to receive(:current_user).and_return(user) }
 
     [Consumer, ExecutionEnvironment, Exercise, FileType, InternalUser].each do |model|
       expect_permitted_path(:"new_#{model.model_name.singular}_path")
@@ -14,7 +15,8 @@ describe 'Authorization' do
 
   context 'as an external user' do
     let(:user) { FactoryBot.create(:external_user) }
-    before(:each) { allow_any_instance_of(ApplicationController).to receive(:current_user).and_return(user) }
+
+    before { allow_any_instance_of(ApplicationController).to receive(:current_user).and_return(user) }
 
     [Consumer, ExecutionEnvironment, Exercise, FileType, InternalUser].each do |model|
       expect_forbidden_path(:"new_#{model.model_name.singular}_path")
@@ -23,7 +25,8 @@ describe 'Authorization' do
 
   context 'as a teacher' do
     let(:user) { FactoryBot.create(:teacher) }
-    before(:each) { allow_any_instance_of(ApplicationController).to receive(:current_user).and_return(user) }
+
+    before { allow_any_instance_of(ApplicationController).to receive(:current_user).and_return(user) }
 
     [Consumer, InternalUser, ExecutionEnvironment, FileType].each do |model|
       expect_forbidden_path(:"new_#{model.model_name.singular}_path")
diff --git a/spec/features/editor_spec.rb b/spec/features/editor_spec.rb
index f43451c8..74436cdc 100644
--- a/spec/features/editor_spec.rb
+++ b/spec/features/editor_spec.rb
@@ -19,7 +19,7 @@ describe 'Editor', js: true do
       score: 1.0,
       filename: 'index.html_spec.rb',
       message: 'Well done.',
-      weight: 2.0
+      weight: 2.0,
     }]
   end
   let(:user) { FactoryBot.create(:teacher) }
@@ -60,7 +60,7 @@ describe 'Editor', js: true do
 
     context 'when selecting a binary file' do
       context 'when selecting an audio file' do
-        let(:file) { exercise.files.detect { |file| file.file_type.audio? } }
+        let(:file) { exercise.files.detect {|file| file.file_type.audio? } }
 
         it 'contains an <audio> tag' do
           expect(page).to have_css("audio[src='#{file.native_file.url}']")
@@ -68,7 +68,7 @@ describe 'Editor', js: true do
       end
 
       context 'when selecting an image file' do
-        let(:file) { exercise.files.detect { |file| file.file_type.image? } }
+        let(:file) { exercise.files.detect {|file| file.file_type.image? } }
 
         it 'contains an <img> tag' do
           expect(page).to have_css("img[src='#{file.native_file.url}']")
@@ -76,7 +76,7 @@ describe 'Editor', js: true do
       end
 
       context 'when selecting a video file' do
-        let(:file) { exercise.files.detect { |file| file.file_type.video? } }
+        let(:file) { exercise.files.detect {|file| file.file_type.video? } }
 
         it 'contains a <video> tag' do
           expect(page).to have_css("video[src='#{file.native_file.url}']")
@@ -85,7 +85,7 @@ describe 'Editor', js: true do
     end
 
     context 'when selecting a non-binary file' do
-      let(:file) { exercise.files.detect { |file| !file.file_type.binary? && !file.hidden? } }
+      let(:file) { exercise.files.detect {|file| !file.file_type.binary? && !file.hidden? } }
 
       it "displays the file's code" do
         expect(page).to have_css(".frame[data-filename='#{file.name_with_extension}']")
diff --git a/spec/features/factories_spec.rb b/spec/features/factories_spec.rb
index cba0d735..4b65cc3d 100644
--- a/spec/features/factories_spec.rb
+++ b/spec/features/factories_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe 'Factories' do
diff --git a/spec/features/prometheus/controller_spec.rb b/spec/features/prometheus/controller_spec.rb
index a0e87885..7aebaeaa 100644
--- a/spec/features/prometheus/controller_spec.rb
+++ b/spec/features/prometheus/controller_spec.rb
@@ -3,7 +3,6 @@
 require 'rails_helper'
 
 describe Prometheus::Controller do
-
   let(:codeocean_config) { instance_double(CodeOcean::Config) }
   let(:prometheus_config) { {prometheus_exporter: {enabled: true}} }
 
diff --git a/spec/features/request_for_comments_filter_spec.rb b/spec/features/request_for_comments_filter_spec.rb
index e2139797..9f264171 100644
--- a/spec/features/request_for_comments_filter_spec.rb
+++ b/spec/features/request_for_comments_filter_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe 'Request_for_Comments' do
diff --git a/spec/helpers/admin/dashboard_helper_spec.rb b/spec/helpers/admin/dashboard_helper_spec.rb
index 9dadaa54..a0594a13 100644
--- a/spec/helpers/admin/dashboard_helper_spec.rb
+++ b/spec/helpers/admin/dashboard_helper_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe Admin::DashboardHelper do
@@ -8,7 +10,7 @@ describe Admin::DashboardHelper do
   end
 
   describe '#docker_data' do
-    before(:each) { FactoryBot.create(:ruby) }
+    before { FactoryBot.create(:ruby) }
 
     it 'contains an entry for every execution environment' do
       expect(docker_data.length).to eq(ExecutionEnvironment.count)
diff --git a/spec/helpers/application_helper_spec.rb b/spec/helpers/application_helper_spec.rb
index e8e9b132..241cae24 100644
--- a/spec/helpers/application_helper_spec.rb
+++ b/spec/helpers/application_helper_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe ApplicationHelper do
diff --git a/spec/helpers/exercise_helper_spec.rb b/spec/helpers/exercise_helper_spec.rb
index 7feb10ca..9fd8feea 100644
--- a/spec/helpers/exercise_helper_spec.rb
+++ b/spec/helpers/exercise_helper_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe ExerciseHelper do
diff --git a/spec/helpers/yaml_spec.rb b/spec/helpers/yaml_spec.rb
index 6518edfd..6222f3a9 100644
--- a/spec/helpers/yaml_spec.rb
+++ b/spec/helpers/yaml_spec.rb
@@ -5,7 +5,7 @@ require 'yaml'
 
 describe 'yaml config files' do
   Find.find(__dir__, 'config') do |path|
-    next unless path =~ /.*.\.yml/
+    next unless /.*.\.yml/.match?(path)
 
     it "loads #{path} without syntax error" do
       expect { YAML.load_file(path) }.not_to raise_error
diff --git a/spec/lib/assessor_spec.rb b/spec/lib/assessor_spec.rb
index ac726c3f..bc340536 100644
--- a/spec/lib/assessor_spec.rb
+++ b/spec/lib/assessor_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe Assessor do
@@ -8,7 +10,7 @@ describe Assessor do
     let(:stdout) { "Finished in 0.1 seconds (files took 0.1 seconds to load)\n2 examples, 1 failure" }
 
     context 'when an error occurs' do
-      before(:each) do
+      before do
         expect_any_instance_of(TestingFrameworkAdapter).to receive(:test_outcome).and_raise
       end
 
@@ -22,7 +24,7 @@ describe Assessor do
     end
 
     context 'when no error occurs' do
-      after(:each) { assess }
+      after { assess }
 
       it 'utilizes the testing framework adapter' do
         expect(assessor.instance_variable_get(:@testing_framework_adapter)).to receive(:test_outcome)
@@ -40,7 +42,7 @@ describe Assessor do
     let(:test_outcome) { {count: count, passed: passed} }
 
     it 'returns the correct score' do
-      expect(assessor.send(:calculate_score, test_outcome)).to eq(passed.to_f / count.to_f)
+      expect(assessor.send(:calculate_score, test_outcome)).to eq(passed.to_f / count)
     end
   end
 
diff --git a/spec/lib/code_ocean/config_spec.rb b/spec/lib/code_ocean/config_spec.rb
index a8aacfab..3309b2fb 100644
--- a/spec/lib/code_ocean/config_spec.rb
+++ b/spec/lib/code_ocean/config_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe CodeOcean::Config do
@@ -10,8 +12,9 @@ describe CodeOcean::Config do
       let(:read) { described_class.new(filename).read }
 
       context 'when the file is present' do
-        before(:each) { File.write(path, {Rails.env.to_s => content}.to_yaml) }
-        after(:each) { FileUtils.rm(path) }
+        before { File.write(path, {Rails.env.to_s => content}.to_yaml) }
+
+        after { FileUtils.rm(path) }
 
         it 'returns the environment-specific content' do
           expect(read).to eq(content.with_indifferent_access)
@@ -30,8 +33,9 @@ describe CodeOcean::Config do
       let(:read) { described_class.new(filename).read(erb: true) }
 
       context 'when the file is present' do
-        before(:each) { File.write(path, {Rails.env.to_s => content}.to_yaml) }
-        after(:each) { FileUtils.rm(path) }
+        before { File.write(path, {Rails.env.to_s => content}.to_yaml) }
+
+        after { FileUtils.rm(path) }
 
         it 'returns the environment-specific content' do
           expect(read).to eq(content.with_indifferent_access)
diff --git a/spec/lib/docker_client_spec.rb b/spec/lib/docker_client_spec.rb
index 06b1faa2..609c0c69 100644
--- a/spec/lib/docker_client_spec.rb
+++ b/spec/lib/docker_client_spec.rb
@@ -1,4 +1,5 @@
 # frozen_string_literal: true
+
 require 'rails_helper'
 require 'seeds_helper'
 
@@ -85,7 +86,7 @@ describe DockerClient, docker: true do
       FileUtils.mkdir_p(workspace_path)
       allow(described_class).to receive(:generate_local_workspace_path).and_return(local_workspace_path)
       expect(described_class).to receive(:container_creation_options).with(execution_environment, local_workspace_path)
-                                     .and_wrap_original do |original_method, *args, &block|
+        .and_wrap_original do |original_method, *args, &block|
         result = original_method.call(*args, &block)
         result['NanoCPUs'] = 2 * 1_000_000_000 # CPU quota in units of 10^-9 CPUs.
         result
@@ -113,7 +114,7 @@ describe DockerClient, docker: true do
       let(:error) { Docker::Error::NotFoundError.new }
 
       context 'when retries are left' do
-        before(:each) do
+        before do
           expect(described_class).to receive(:mapped_directories).and_raise(error).and_call_original
         end
 
@@ -123,7 +124,7 @@ describe DockerClient, docker: true do
       end
 
       context 'when no retries are left' do
-        before(:each) do
+        before do
           expect(described_class).to receive(:mapped_directories).exactly(DockerClient::RETRY_COUNT + 1).times.and_raise(error)
         end
 
@@ -138,24 +139,24 @@ describe DockerClient, docker: true do
   describe '#create_workspace_files' do
     let(:container) { double }
 
-    before(:each) do
+    before do
       expect(container).to receive(:binds).at_least(:once).and_return(["#{workspace_path}:#{DockerClient::CONTAINER_WORKSPACE_PATH}"])
     end
 
-    after(:each) { docker_client.send(:create_workspace_files, container, submission) }
+    after { docker_client.send(:create_workspace_files, container, submission) }
 
     it 'creates submission-specific directories' do
       expect(Dir).to receive(:mkdir).at_least(:once).and_call_original
     end
 
     it 'copies binary files' do
-      submission.collect_files.select { |file| file.file_type.binary? }.each do |file|
+      submission.collect_files.select {|file| file.file_type.binary? }.each do |file|
         expect(docker_client).to receive(:copy_file_to_workspace).with(container: container, file: file)
       end
     end
 
     it 'creates non-binary files' do
-      submission.collect_files.reject { |file| file.file_type.binary? }.each do |file|
+      submission.collect_files.reject {|file| file.file_type.binary? }.each do |file|
         expect(docker_client).to receive(:create_workspace_file).with(container: container, file: file)
       end
     end
@@ -164,7 +165,8 @@ describe DockerClient, docker: true do
   describe '#create_workspace_file' do
     let(:file) { FactoryBot.build(:file, content: 'puts 42') }
     let(:file_path) { File.join(workspace_path, file.name_with_extension) }
-    after(:each) { File.delete(file_path) }
+
+    after { File.delete(file_path) }
 
     it 'creates a file' do
       expect(described_class).to receive(:local_workspace_path).at_least(:once).and_return(workspace_path)
@@ -177,7 +179,8 @@ describe DockerClient, docker: true do
 
   describe '.destroy_container' do
     let(:container) { described_class.create_container(execution_environment) }
-    after(:each) { described_class.destroy_container(container) }
+
+    after { described_class.destroy_container(container) }
 
     it 'kills running processes' do
       expect(container).to receive(:kill).and_return(container)
@@ -190,8 +193,8 @@ describe DockerClient, docker: true do
 
     it 'removes the mapped directory' do
       expect(described_class).to receive(:local_workspace_path).at_least(:once).and_return(workspace_path)
-      #!TODO Fix this
-      #expect(PathName).to receive(:rmtree).with(workspace_path)
+      # !TODO Fix this
+      # expect(PathName).to receive(:rmtree).with(workspace_path)
     end
 
     it 'deletes the container' do
@@ -216,9 +219,9 @@ describe DockerClient, docker: true do
       let(:error) { Excon::Errors::SocketError.new(SocketError.new) }
 
       context 'when retries are left' do
-        let(:result) { {status: "ok", stdout: 42} }
+        let(:result) { {status: 'ok', stdout: 42} }
 
-        before(:each) do
+        before do
           expect(docker_client).to receive(:send_command).and_raise(error).and_return(result)
         end
 
@@ -228,43 +231,45 @@ describe DockerClient, docker: true do
       end
 
       context 'when no retries are left' do
-        before(:each) do
+        before do
           expect(docker_client).to receive(:send_command).exactly(DockerClient::RETRY_COUNT + 1).times.and_raise(error)
         end
 
         it 'raises the error' do
-          pending("retries are disabled")
-          #!TODO Retries is disabled
-          #expect { execute_arbitrary_command }.to raise_error(error)
+          pending('retries are disabled')
+          # !TODO Retries is disabled
+          # expect { execute_arbitrary_command }.to raise_error(error)
         end
       end
     end
   end
 
   describe '#execute_run_command' do
-    let(:filename) { submission.exercise.files.detect { |file| file.role == 'main_file' }.name_with_extension }
-    after(:each) { docker_client.send(:execute_run_command, submission, filename) }
+    let(:filename) { submission.exercise.files.detect {|file| file.role == 'main_file' }.name_with_extension }
+
+    after { docker_client.send(:execute_run_command, submission, filename) }
 
     it 'takes a container from the pool' do
-      pending("todo in the future")
+      pending('todo in the future')
       expect(DockerContainerPool).to receive(:get_container).with(submission.execution_environment).and_call_original
     end
 
     it 'creates the workspace files' do
-      pending("todo in the future")
+      pending('todo in the future')
       expect(docker_client).to receive(:create_workspace_files)
     end
 
     it 'executes the run command' do
-      pending("todo in the future")
+      pending('todo in the future')
       expect(submission.execution_environment).to receive(:run_command).and_call_original
       expect(docker_client).to receive(:send_command).with(kind_of(String), kind_of(Docker::Container))
     end
   end
 
   describe '#execute_test_command' do
-    let(:filename) { submission.exercise.files.detect { |file| file.role == 'teacher_defined_test' || file.role == 'teacher_defined_linter' }.name_with_extension }
-    after(:each) { docker_client.send(:execute_test_command, submission, filename) }
+    let(:filename) { submission.exercise.files.detect {|file| file.role == 'teacher_defined_test' || file.role == 'teacher_defined_linter' }.name_with_extension }
+
+    after { docker_client.send(:execute_test_command, submission, filename) }
 
     it 'takes a container from the pool' do
       expect(DockerContainerPool).to receive(:get_container).with(submission.execution_environment).and_call_original
@@ -300,7 +305,7 @@ describe DockerClient, docker: true do
     end
 
     context 'with incomplete configuration' do
-      before(:each) { expect(described_class).to receive(:config).at_least(:once).and_return({}) }
+      before { expect(described_class).to receive(:config).at_least(:once).and_return({}) }
 
       it 'raises an error' do
         expect { described_class.initialize_environment }.to raise_error(DockerClient::Error)
@@ -331,7 +336,7 @@ describe DockerClient, docker: true do
 
   describe '.mapped_ports' do
     context 'with exposed ports' do
-      before(:each) { execution_environment.exposed_ports = '3000' }
+      before { execution_environment.exposed_ports = '3000' }
 
       it 'returns a mapping' do
         expect(described_class.mapped_ports(execution_environment)).to be_a(Hash)
@@ -355,30 +360,31 @@ describe DockerClient, docker: true do
     let(:block) { proc {} }
     let(:container) { described_class.create_container(execution_environment) }
     let(:send_command) { docker_client.send(:send_command, command, container, &block) }
-    after(:each) { send_command }
+
+    after { send_command }
 
     it 'limits the execution time' do
       expect(Timeout).to receive(:timeout).at_least(:once).with(kind_of(Numeric)).and_call_original
     end
 
     it 'provides the command to be executed as input' do
-      pending("we are currently not using any input and for output server send events instead of attach.")
+      pending('we are currently not using any input and for output server send events instead of attach.')
       expect(container).to receive(:attach).with(stdin: kind_of(StringIO))
     end
 
     it 'calls the block' do
-      pending("block is no longer called, see revision 4cbf9970b13362efd4588392cafe4f7fd7cb31c3 to get information how it was done before.")
+      pending('block is no longer called, see revision 4cbf9970b13362efd4588392cafe4f7fd7cb31c3 to get information how it was done before.')
       expect(block).to receive(:call)
     end
 
     context 'when a timeout occurs' do
-      before(:each) do
+      before do
         expect(container).to receive(:exec).once.and_raise(Timeout::Error)
         expect(container).to receive(:exec).twice.and_return([[], []])
       end
 
       it 'destroys the container asynchronously' do
-        pending("Container is destroyed, but not as expected in this test. ToDo update this test.")
+        pending('Container is destroyed, but not as expected in this test. ToDo update this test.')
         expect(Concurrent::Future).to receive(:execute)
       end
 
@@ -389,7 +395,7 @@ describe DockerClient, docker: true do
 
     context 'when the container terminates timely' do
       it 'destroys the container asynchronously' do
-        pending("Container is destroyed, but not as expected in this test. ToDo update this test.")
+        pending('Container is destroyed, but not as expected in this test. ToDo update this test.')
         expect(Concurrent::Future).to receive(:execute)
       end
 
diff --git a/spec/lib/docker_container_mixin_spec.rb b/spec/lib/docker_container_mixin_spec.rb
index 2ae95e50..6a3f04f3 100644
--- a/spec/lib/docker_container_mixin_spec.rb
+++ b/spec/lib/docker_container_mixin_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe DockerContainerMixin do
diff --git a/spec/lib/file_tree_spec.rb b/spec/lib/file_tree_spec.rb
index f89e016d..53361d79 100644
--- a/spec/lib/file_tree_spec.rb
+++ b/spec/lib/file_tree_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe FileTree do
@@ -161,7 +163,7 @@ describe FileTree do
 
     context 'for intermediary nodes' do
       let(:node) do
-        root.add(Tree::TreeNode.new('').tap { |node| node.add(Tree::TreeNode.new('')) })
+        root.add(Tree::TreeNode.new('').tap {|node| node.add(Tree::TreeNode.new('')) })
       end
 
       it 'is a folder icon' do
diff --git a/spec/lib/generators/testing_framework_adapter_generator_spec.rb b/spec/lib/generators/testing_framework_adapter_generator_spec.rb
index 36db453d..ed4ab02b 100644
--- a/spec/lib/generators/testing_framework_adapter_generator_spec.rb
+++ b/spec/lib/generators/testing_framework_adapter_generator_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails/generators'
 require 'generators/testing_framework_adapter_generator'
 require 'rails_helper'
@@ -10,11 +12,11 @@ describe TestingFrameworkAdapterGenerator do
     let(:path) { Rails.root.join('lib', "#{name.underscore}_adapter.rb") }
     let(:spec_path) { Rails.root.join('spec', 'lib', "#{name.underscore}_adapter_spec.rb") }
 
-    before(:each) do
+    before do
       silenced { Rails::Generators.invoke('testing_framework_adapter', [name]) }
     end
 
-    after(:each) do
+    after do
       File.delete(path)
       File.delete(spec_path)
     end
diff --git a/spec/lib/junit_adapter_spec.rb b/spec/lib/junit_adapter_spec.rb
index 5383219a..ebde0904 100644
--- a/spec/lib/junit_adapter_spec.rb
+++ b/spec/lib/junit_adapter_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe JunitAdapter do
diff --git a/spec/lib/mocha_adapter_spec.rb b/spec/lib/mocha_adapter_spec.rb
index ed3b1685..e6974e19 100644
--- a/spec/lib/mocha_adapter_spec.rb
+++ b/spec/lib/mocha_adapter_spec.rb
@@ -1,10 +1,12 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe MochaAdapter do
   let(:adapter) { described_class.new }
   let(:count) { 42 }
   let(:failed) { 25 }
-  let(:stdout) { "#{count-failed} passing (20ms)\n\n#{failed} failing" }
+  let(:stdout) { "#{count - failed} passing (20ms)\n\n#{failed} failing" }
 
   describe '#parse_output' do
     it 'returns the correct numbers' do
diff --git a/spec/lib/nonce_store_spec.rb b/spec/lib/nonce_store_spec.rb
index 8b32726e..145037dd 100644
--- a/spec/lib/nonce_store_spec.rb
+++ b/spec/lib/nonce_store_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe NonceStore do
diff --git a/spec/lib/port_pool_spec.rb b/spec/lib/port_pool_spec.rb
index c638cb09..3294c106 100644
--- a/spec/lib/port_pool_spec.rb
+++ b/spec/lib/port_pool_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe PortPool do
diff --git a/spec/lib/py_unit_adapter_spec.rb b/spec/lib/py_unit_adapter_spec.rb
index f5ba71d6..04c8f723 100644
--- a/spec/lib/py_unit_adapter_spec.rb
+++ b/spec/lib/py_unit_adapter_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe PyUnitAdapter do
diff --git a/spec/lib/rspec_adapter_spec.rb b/spec/lib/rspec_adapter_spec.rb
index ce52651a..e3f30c6b 100644
--- a/spec/lib/rspec_adapter_spec.rb
+++ b/spec/lib/rspec_adapter_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe RspecAdapter do
diff --git a/spec/lib/sql_result_set_comparator_adapter_spec.rb b/spec/lib/sql_result_set_comparator_adapter_spec.rb
index 88b2dea8..e31fff87 100644
--- a/spec/lib/sql_result_set_comparator_adapter_spec.rb
+++ b/spec/lib/sql_result_set_comparator_adapter_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe SqlResultSetComparatorAdapter do
diff --git a/spec/lib/testing_framework_adapter_spec.rb b/spec/lib/testing_framework_adapter_spec.rb
index f09d0778..77a7210d 100644
--- a/spec/lib/testing_framework_adapter_spec.rb
+++ b/spec/lib/testing_framework_adapter_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe TestingFrameworkAdapter do
diff --git a/spec/mailers/previews/user_mailer_preview.rb b/spec/mailers/previews/user_mailer_preview.rb
index a3770fda..bcd06a72 100644
--- a/spec/mailers/previews/user_mailer_preview.rb
+++ b/spec/mailers/previews/user_mailer_preview.rb
@@ -1,5 +1,7 @@
+# frozen_string_literal: true
+
 class UserMailerPreview < ActionMailer::Preview
-  def exercise_anomaly_detected()
+  def exercise_anomaly_detected
     collection = ExerciseCollection.new(name: 'Hello World', user: FactoryBot.create(:admin))
     anomalies = {49 => 879.325828, 51 => 924.870057, 31 => 1031.21233, 69 => 2159.182116}
     UserMailer.exercise_anomaly_detected(collection, anomalies)
diff --git a/spec/mailers/user_mailer_spec.rb b/spec/mailers/user_mailer_spec.rb
index 59962280..5054abd8 100644
--- a/spec/mailers/user_mailer_spec.rb
+++ b/spec/mailers/user_mailer_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe UserMailer do
@@ -6,7 +8,7 @@ describe UserMailer do
   describe '#activation_needed_email' do
     let(:mail) { described_class.activation_needed_email(user) }
 
-    before(:each) do
+    before do
       user.send(:setup_activation)
       user.save(validate: false)
     end
@@ -37,7 +39,7 @@ describe UserMailer do
   describe '#reset_password_email' do
     let(:mail) { described_class.reset_password_email(user) }
 
-    before(:each) do
+    before do
       user.send(:setup_activation)
       user.save(validate: false)
     end
diff --git a/spec/models/code_ocean/file_spec.rb b/spec/models/code_ocean/file_spec.rb
index 1f0524a2..514ce987 100644
--- a/spec/models/code_ocean/file_spec.rb
+++ b/spec/models/code_ocean/file_spec.rb
@@ -1,7 +1,9 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe CodeOcean::File do
-  let(:file) { described_class.create.tap { |file| file.update(content: nil, hidden: nil, read_only: nil) } }
+  let(:file) { described_class.create.tap {|file| file.update(content: nil, hidden: nil, read_only: nil) } }
 
   it 'validates the presence of a file type' do
     expect(file.errors[:file_type_id]).to be_present
@@ -24,7 +26,7 @@ describe CodeOcean::File do
   end
 
   context 'as a teacher-defined test' do
-    before(:each) { file.update(role: 'teacher_defined_test') }
+    before { file.update(role: 'teacher_defined_test') }
 
     it 'validates the presence of a feedback message' do
       expect(file.errors[:feedback_message]).to be_present
@@ -41,7 +43,7 @@ describe CodeOcean::File do
   end
 
   context 'with another file type' do
-    before(:each) { file.update(role: 'regular_file') }
+    before { file.update(role: 'regular_file') }
 
     it 'validates the absence of a feedback message' do
       file.update(feedback_message: 'Your solution is not correct yet.')
diff --git a/spec/models/codeharbor_link_spec.rb b/spec/models/codeharbor_link_spec.rb
index df1ddba4..f999164e 100644
--- a/spec/models/codeharbor_link_spec.rb
+++ b/spec/models/codeharbor_link_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe CodeharborLink do
diff --git a/spec/models/consumer_spec.rb b/spec/models/consumer_spec.rb
index 0c977955..8ffb7b2d 100644
--- a/spec/models/consumer_spec.rb
+++ b/spec/models/consumer_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe Consumer do
diff --git a/spec/models/execution_environment_spec.rb b/spec/models/execution_environment_spec.rb
index fc119b38..396cbd96 100644
--- a/spec/models/execution_environment_spec.rb
+++ b/spec/models/execution_environment_spec.rb
@@ -1,7 +1,9 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe ExecutionEnvironment do
-  let(:execution_environment) { described_class.create.tap { |execution_environment| execution_environment.update(network_enabled: nil) } }
+  let(:execution_environment) { described_class.create.tap {|execution_environment| execution_environment.update(network_enabled: nil) } }
 
   it 'validates that the Docker image works', docker: true do
     expect(execution_environment).to receive(:validate_docker_image?).and_return(true)
@@ -69,7 +71,7 @@ describe ExecutionEnvironment do
 
   describe '#valid_test_setup?' do
     context 'with a test command and a testing framework' do
-      before(:each) { execution_environment.update(test_command: FactoryBot.attributes_for(:ruby)[:test_command], testing_framework: FactoryBot.attributes_for(:ruby)[:testing_framework]) }
+      before { execution_environment.update(test_command: FactoryBot.attributes_for(:ruby)[:test_command], testing_framework: FactoryBot.attributes_for(:ruby)[:testing_framework]) }
 
       it 'is valid' do
         expect(execution_environment.errors[:test_command]).to be_blank
@@ -77,7 +79,7 @@ describe ExecutionEnvironment do
     end
 
     context 'with a test command but no testing framework' do
-      before(:each) { execution_environment.update(test_command: FactoryBot.attributes_for(:ruby)[:test_command], testing_framework: nil) }
+      before { execution_environment.update(test_command: FactoryBot.attributes_for(:ruby)[:test_command], testing_framework: nil) }
 
       it 'is invalid' do
         expect(execution_environment.errors[:test_command]).to be_present
@@ -85,7 +87,7 @@ describe ExecutionEnvironment do
     end
 
     context 'with no test command but a testing framework' do
-      before(:each) { execution_environment.update(test_command: nil, testing_framework: FactoryBot.attributes_for(:ruby)[:testing_framework]) }
+      before { execution_environment.update(test_command: nil, testing_framework: FactoryBot.attributes_for(:ruby)[:testing_framework]) }
 
       it 'is invalid' do
         expect(execution_environment.errors[:test_command]).to be_present
@@ -93,7 +95,7 @@ describe ExecutionEnvironment do
     end
 
     context 'with no test command and no testing framework' do
-      before(:each) { execution_environment.update(test_command: nil, testing_framework: nil) }
+      before { execution_environment.update(test_command: nil, testing_framework: nil) }
 
       it 'is valid' do
         expect(execution_environment.errors[:test_command]).to be_blank
@@ -121,7 +123,8 @@ describe ExecutionEnvironment do
 
   describe '#working_docker_image?', docker: true do
     let(:working_docker_image?) { execution_environment.send(:working_docker_image?) }
-    before(:each) { expect(DockerClient).to receive(:find_image_by_tag).and_return(Object.new) }
+
+    before { expect(DockerClient).to receive(:find_image_by_tag).and_return(Object.new) }
 
     it 'instantiates a Docker client' do
       expect(DockerClient).to receive(:new).with(execution_environment: execution_environment).and_call_original
diff --git a/spec/models/exercise_spec.rb b/spec/models/exercise_spec.rb
index 3576d3a5..c10b88d9 100644
--- a/spec/models/exercise_spec.rb
+++ b/spec/models/exercise_spec.rb
@@ -1,13 +1,13 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe Exercise do
-  let(:exercise) { described_class.create.tap { |exercise| exercise.update(public: nil, token: nil) } }
+  let(:exercise) { described_class.create.tap {|exercise| exercise.update(public: nil, token: nil) } }
   let(:users) { FactoryBot.create_list(:external_user, 10) }
 
   def create_submissions
-    10.times do
-      FactoryBot.create(:submission, cause: 'submit', exercise: exercise, score: Forgery(:basic).number, user: users.sample)
-    end
+    FactoryBot.create_list(:submission, 10, cause: 'submit', exercise: exercise, score: Forgery(:basic).number, user: users.sample)
   end
 
   it 'validates the number of main files' do
@@ -75,10 +75,10 @@ describe Exercise do
     end
 
     context 'with submissions' do
-      before(:each) { create_submissions }
+      before { create_submissions }
 
       it 'returns the average score expressed as a percentage' do
-        maximum_percentages = exercise.submissions.group_by(&:user_id).values.map { |submission| submission.sort_by(&:score).last.score / exercise.maximum_score * 100 }
+        maximum_percentages = exercise.submissions.group_by(&:user_id).values.map {|submission| submission.max_by(&:score).score / exercise.maximum_score * 100 }
         expect(exercise.average_percentage).to eq(maximum_percentages.average.round(2))
       end
     end
@@ -94,10 +94,10 @@ describe Exercise do
     end
 
     context 'with submissions' do
-      before(:each) { create_submissions }
+      before { create_submissions }
 
       it "returns the average of all users' maximum scores" do
-        maximum_scores = exercise.submissions.group_by(&:user_id).values.map { |submission| submission.sort_by(&:score).last.score }
+        maximum_scores = exercise.submissions.group_by(&:user_id).values.map {|submission| submission.max_by(&:score).score }
         expect(exercise.average_score).to be_within(0.1).of(maximum_scores.average)
       end
     end
@@ -105,7 +105,8 @@ describe Exercise do
 
   describe '#duplicate' do
     let(:exercise) { FactoryBot.create(:fibonacci) }
-    after(:each) { exercise.duplicate }
+
+    after { exercise.duplicate }
 
     it 'duplicates the exercise' do
       expect(exercise).to receive(:dup).and_call_original
diff --git a/spec/models/external_user_spec.rb b/spec/models/external_user_spec.rb
index 5d1d0aae..ee7ca64b 100644
--- a/spec/models/external_user_spec.rb
+++ b/spec/models/external_user_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe ExternalUser do
diff --git a/spec/models/file_type_spec.rb b/spec/models/file_type_spec.rb
index 0193a9fd..4fb00c1f 100644
--- a/spec/models/file_type_spec.rb
+++ b/spec/models/file_type_spec.rb
@@ -1,7 +1,9 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe FileType do
-  let(:file_type) { described_class.create.tap { |file_type| file_type.update(binary: nil, executable: nil, renderable: nil) } }
+  let(:file_type) { described_class.create.tap {|file_type| file_type.update(binary: nil, executable: nil, renderable: nil) } }
 
   it 'validates the presence of the binary flag' do
     expect(file_type.errors[:binary]).to be_present
@@ -10,7 +12,7 @@ describe FileType do
   end
 
   context 'when binary' do
-    before(:each) { file_type.update(binary: true) }
+    before { file_type.update(binary: true) }
 
     it 'does not validate the presence of an editor mode' do
       expect(file_type.errors[:editor_mode]).not_to be_present
@@ -22,7 +24,7 @@ describe FileType do
   end
 
   context 'when not binary' do
-    before(:each) { file_type.update(binary: false) }
+    before { file_type.update(binary: false) }
 
     it 'validates the presence of an editor mode' do
       expect(file_type.errors[:editor_mode]).to be_present
diff --git a/spec/models/internal_user_spec.rb b/spec/models/internal_user_spec.rb
index 25f7e172..a9c131be 100644
--- a/spec/models/internal_user_spec.rb
+++ b/spec/models/internal_user_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe InternalUser do
@@ -16,7 +18,7 @@ describe InternalUser do
   context 'when not activated' do
     let(:user) { FactoryBot.create(:teacher) }
 
-    before(:each) do
+    before do
       user.send(:setup_activation)
       user.send(:send_activation_needed_email!)
     end
@@ -34,7 +36,8 @@ describe InternalUser do
 
   context 'with a pending password reset' do
     let(:user) { FactoryBot.create(:teacher) }
-    before(:each) { user.deliver_reset_password_instructions! }
+
+    before { user.deliver_reset_password_instructions! }
 
     it 'validates the confirmation of the password' do
       user.update(password: password, password_confirmation: '')
diff --git a/spec/models/submission_spec.rb b/spec/models/submission_spec.rb
index 17ea63fb..89f6d5ce 100644
--- a/spec/models/submission_spec.rb
+++ b/spec/models/submission_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe Submission do
@@ -28,7 +30,8 @@ describe Submission do
   describe '#normalized_score' do
     context 'with a score' do
       let(:submission) { FactoryBot.create(:submission) }
-      before(:each) { submission.score = submission.exercise.maximum_score / 2 }
+
+      before { submission.score = submission.exercise.maximum_score / 2 }
 
       it 'returns the score as a value between 0 and 1' do
         expect(0..1).to include(submission.normalized_score)
@@ -36,7 +39,7 @@ describe Submission do
     end
 
     context 'without a score' do
-      before(:each) { submission.score = nil }
+      before { submission.score = nil }
 
       it 'returns 0' do
         expect(submission.normalized_score).to be 0
@@ -47,7 +50,8 @@ describe Submission do
   describe '#percentage' do
     context 'with a score' do
       let(:submission) { FactoryBot.create(:submission) }
-      before(:each) { submission.score = submission.exercise.maximum_score / 2 }
+
+      before { submission.score = submission.exercise.maximum_score / 2 }
 
       it 'returns the score expressed as a percentage' do
         expect(0..100).to include(submission.percentage)
@@ -55,7 +59,7 @@ describe Submission do
     end
 
     context 'without a score' do
-      before(:each) { submission.score = nil }
+      before { submission.score = nil }
 
       it 'returns 0' do
         expect(submission.percentage).to be 0
@@ -67,7 +71,7 @@ describe Submission do
     let(:siblings) { described_class.find_by(user: user).siblings }
     let(:user) { FactoryBot.create(:external_user) }
 
-    before(:each) do
+    before do
       10.times.each_with_index do |_, index|
         FactoryBot.create(:submission, exercise: submission.exercise, user: (index.even? ? user : FactoryBot.create(:external_user)))
       end
@@ -87,11 +91,10 @@ describe Submission do
   end
 
   describe '#redirect_to_feedback?' do
-
     context 'with no exercise feedback' do
-      let(:exercise) {FactoryBot.create(:dummy)}
-      let(:user) {FactoryBot.build(:external_user, id: (11 - exercise.created_at.to_i % 10) % 10)}
-      let(:submission) {FactoryBot.build(:submission, exercise: exercise, user: user)}
+      let(:exercise) { FactoryBot.create(:dummy) }
+      let(:user) { FactoryBot.build(:external_user, id: (11 - exercise.created_at.to_i % 10) % 10) }
+      let(:submission) { FactoryBot.build(:submission, exercise: exercise, user: user) }
 
       it 'sends 10% of users to feedback page' do
         expect(submission.send(:redirect_to_feedback?)).to be_truthy
@@ -106,9 +109,9 @@ describe Submission do
     end
 
     context 'with little exercise feedback' do
-      let(:exercise) {FactoryBot.create(:dummy_with_user_feedbacks)}
-      let(:user) {FactoryBot.build(:external_user, id: (11 - exercise.created_at.to_i % 10) % 10)}
-      let(:submission) {FactoryBot.build(:submission, exercise: exercise, user: user)}
+      let(:exercise) { FactoryBot.create(:dummy_with_user_feedbacks) }
+      let(:user) { FactoryBot.build(:external_user, id: (11 - exercise.created_at.to_i % 10) % 10) }
+      let(:submission) { FactoryBot.build(:submission, exercise: exercise, user: user) }
 
       it 'sends 10% of users to feedback page' do
         expect(submission.send(:redirect_to_feedback?)).to be_truthy
@@ -123,15 +126,15 @@ describe Submission do
     end
 
     context 'with enough exercise feedback' do
-      let(:exercise) {FactoryBot.create(:dummy_with_user_feedbacks, user_feedbacks_count: 42)}
-      let(:user) {FactoryBot.create(:external_user)}
+      let(:exercise) { FactoryBot.create(:dummy_with_user_feedbacks, user_feedbacks_count: 42) }
+      let(:user) { FactoryBot.create(:external_user) }
 
       before do
         allow_any_instance_of(described_class).to receive(:redirect_to_feedback?).and_return(false)
       end
 
       it 'sends nobody to feedback page' do
-        30.times do |i|
+        30.times do |_i|
           submission = FactoryBot.create(:submission, exercise: exercise, user: FactoryBot.create(:external_user))
           expect(submission.send(:redirect_to_feedback?)).to be_falsey
         end
diff --git a/spec/policies/admin/dashboard_policy_spec.rb b/spec/policies/admin/dashboard_policy_spec.rb
index 71a7adcd..a4a7a4de 100644
--- a/spec/policies/admin/dashboard_policy_spec.rb
+++ b/spec/policies/admin/dashboard_policy_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe Admin::DashboardPolicy do
diff --git a/spec/policies/application_policy_spec.rb b/spec/policies/application_policy_spec.rb
index 6ab7864a..b58f137b 100644
--- a/spec/policies/application_policy_spec.rb
+++ b/spec/policies/application_policy_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe ApplicationPolicy do
diff --git a/spec/policies/code_ocean/file_policy_spec.rb b/spec/policies/code_ocean/file_policy_spec.rb
index 276ded5f..8f65e928 100644
--- a/spec/policies/code_ocean/file_policy_spec.rb
+++ b/spec/policies/code_ocean/file_policy_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe CodeOcean::FilePolicy do
@@ -19,7 +21,7 @@ describe CodeOcean::FilePolicy do
       end
 
       it 'does not grant access to all other users' do
-        [:external_user, :teacher].each do |factory_name|
+        %i[external_user teacher].each do |factory_name|
           expect(subject).not_to permit(FactoryBot.build(factory_name), file)
         end
       end
@@ -49,7 +51,7 @@ describe CodeOcean::FilePolicy do
       end
 
       it 'does not grant access to all other users' do
-        [:admin, :external_user, :teacher].each do |factory_name|
+        %i[admin external_user teacher].each do |factory_name|
           expect(subject).not_to permit(FactoryBot.build(factory_name), file)
         end
       end
@@ -69,7 +71,7 @@ describe CodeOcean::FilePolicy do
       end
 
       it 'does not grant access to all other users' do
-        [:external_user, :teacher].each do |factory_name|
+        %i[external_user teacher].each do |factory_name|
           expect(subject).not_to permit(FactoryBot.build(factory_name), file)
         end
       end
@@ -79,7 +81,7 @@ describe CodeOcean::FilePolicy do
       let(:file) { submission.files.first }
 
       it 'does not grant access to anyone' do
-        [:admin, :external_user, :teacher].each do |factory_name|
+        %i[admin external_user teacher].each do |factory_name|
           expect(subject).not_to permit(FactoryBot.build(factory_name), file)
         end
       end
diff --git a/spec/policies/consumer_policy_spec.rb b/spec/policies/consumer_policy_spec.rb
index 36f96288..832f6201 100644
--- a/spec/policies/consumer_policy_spec.rb
+++ b/spec/policies/consumer_policy_spec.rb
@@ -1,13 +1,15 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe ConsumerPolicy do
   subject { described_class }
 
-  [:create?, :destroy?, :edit?, :index?, :new?, :show?, :update?].each do |action|
+  %i[create? destroy? edit? index? new? show? update?].each do |action|
     permissions(action) do
       it 'grants access to admins only' do
         expect(subject).to permit(FactoryBot.build(:admin), Consumer.new)
-        [:external_user, :teacher].each do |factory_name|
+        %i[external_user teacher].each do |factory_name|
           expect(subject).not_to permit(FactoryBot.build(factory_name), Consumer.new)
         end
       end
diff --git a/spec/policies/execution_environment_policy_spec.rb b/spec/policies/execution_environment_policy_spec.rb
index 50bd57ab..d640f2e8 100644
--- a/spec/policies/execution_environment_policy_spec.rb
+++ b/spec/policies/execution_environment_policy_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe ExecutionEnvironmentPolicy do
@@ -21,7 +23,7 @@ describe ExecutionEnvironmentPolicy do
     end
   end
 
-  [:execute_command?, :shell?, :statistics?, :show?].each do |action|
+  %i[execute_command? shell? statistics? show?].each do |action|
     permissions(action) do
       it 'grants access to admins' do
         expect(subject).to permit(FactoryBot.build(:admin), execution_environment)
@@ -32,14 +34,14 @@ describe ExecutionEnvironmentPolicy do
       end
 
       it 'does not grant access to all other users' do
-        [:external_user, :teacher].each do |factory_name|
+        %i[external_user teacher].each do |factory_name|
           expect(subject).not_to permit(FactoryBot.build(factory_name), execution_environment)
         end
       end
     end
   end
 
-  [:destroy?, :edit?, :update?, :new?, :create?].each do |action|
+  %i[destroy? edit? update? new? create?].each do |action|
     permissions(action) do
       it 'grants access to admins' do
         expect(subject).to permit(FactoryBot.build(:admin), execution_environment)
@@ -50,7 +52,7 @@ describe ExecutionEnvironmentPolicy do
       end
 
       it 'does not grant access to all other users' do
-        [:external_user, :teacher].each do |factory_name|
+        %i[external_user teacher].each do |factory_name|
           expect(subject).not_to permit(FactoryBot.build(factory_name), execution_environment)
         end
       end
diff --git a/spec/policies/exercise_policy_spec.rb b/spec/policies/exercise_policy_spec.rb
index adb73170..b01d3688 100644
--- a/spec/policies/exercise_policy_spec.rb
+++ b/spec/policies/exercise_policy_spec.rb
@@ -1,20 +1,22 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe ExercisePolicy do
   subject { described_class }
 
-let(:exercise) { FactoryBot.build(:dummy, public: true) }
+  let(:exercise) { FactoryBot.build(:dummy, public: true) }
 
   permissions :batch_update? do
     it 'grants access to admins only' do
       expect(subject).to permit(FactoryBot.build(:admin), exercise)
-      [:external_user, :teacher].each do |factory_name|
+      %i[external_user teacher].each do |factory_name|
         expect(subject).not_to permit(FactoryBot.build(factory_name), exercise)
       end
     end
   end
 
-  [:create?, :index?, :new?, :statistics?, :feedback?, :get_rfcs_for_exercise?].each do |action|
+  %i[create? index? new? statistics? feedback? get_rfcs_for_exercise?].each do |action|
     permissions(action) do
       it 'grants access to admins' do
         expect(subject).to permit(FactoryBot.build(:admin), exercise)
@@ -30,7 +32,7 @@ let(:exercise) { FactoryBot.build(:dummy, public: true) }
     end
   end
 
-  [:clone?, :destroy?, :edit?, :update?].each do |action|
+  %i[clone? destroy? edit? update?].each do |action|
     permissions(action) do
       it 'grants access to admins' do
         expect(subject).to permit(FactoryBot.build(:admin), exercise)
@@ -41,14 +43,14 @@ let(:exercise) { FactoryBot.build(:dummy, public: true) }
       end
 
       it 'does not grant access to all other users' do
-        [:external_user, :teacher].each do |factory_name|
+        %i[external_user teacher].each do |factory_name|
           expect(subject).not_to permit(FactoryBot.build(factory_name), exercise)
         end
       end
     end
   end
 
-  [:export_external_check?, :export_external_confirm?].each do |action|
+  %i[export_external_check? export_external_confirm?].each do |action|
     permissions(action) do
       context 'when user is author' do
         let(:user) { exercise.author }
@@ -82,7 +84,7 @@ let(:exercise) { FactoryBot.build(:dummy, public: true) }
         end
       end
 
-      [:external_user, :teacher].each do |factory_name|
+      %i[external_user teacher].each do |factory_name|
         context "when user is #{factory_name}" do
           let(:user) { FactoryBot.build(factory_name) }
 
@@ -110,10 +112,10 @@ let(:exercise) { FactoryBot.build(:dummy, public: true) }
     end
   end
 
-  [:implement?, :submit?].each do |action|
+  %i[implement? submit?].each do |action|
     permissions(action) do
       it 'grants access to anyone' do
-        [:admin, :external_user, :teacher].each do |factory_name|
+        %i[admin external_user teacher].each do |factory_name|
           expect(subject).to permit(FactoryBot.build(factory_name), Exercise.new)
         end
       end
@@ -151,7 +153,6 @@ let(:exercise) { FactoryBot.build(:dummy, public: true) }
       end
 
       context 'for teachers' do
-
         let(:scope) { Pundit.policy_scope!(@teacher, Exercise) }
 
         it 'includes all public exercises' do
diff --git a/spec/policies/external_user_policy_spec.rb b/spec/policies/external_user_policy_spec.rb
index 5d1e468c..d907e209 100644
--- a/spec/policies/external_user_policy_spec.rb
+++ b/spec/policies/external_user_policy_spec.rb
@@ -1,13 +1,15 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe ExternalUserPolicy do
   subject { described_class }
 
-  [:create?, :destroy?, :edit?, :new?, :show?, :update?].each do |action|
+  %i[create? destroy? edit? new? show? update?].each do |action|
     permissions(action) do
       it 'grants access to admins only' do
         expect(subject).to permit(FactoryBot.build(:admin), ExternalUser.new)
-        [:external_user, :teacher].each do |factory_name|
+        %i[external_user teacher].each do |factory_name|
           expect(subject).not_to permit(FactoryBot.build(factory_name), ExternalUser.new)
         end
       end
diff --git a/spec/policies/file_type_policy_spec.rb b/spec/policies/file_type_policy_spec.rb
index 951512d5..f3e6edff 100644
--- a/spec/policies/file_type_policy_spec.rb
+++ b/spec/policies/file_type_policy_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe FileTypePolicy do
@@ -5,7 +7,7 @@ describe FileTypePolicy do
 
   let(:file_type) { FactoryBot.build(:dot_rb) }
 
-  [:destroy?, :edit?, :update?, :new?, :create?, :index?, :show?].each do |action|
+  %i[destroy? edit? update? new? create? index? show?].each do |action|
     permissions(action) do
       it 'grants access to admins' do
         expect(subject).to permit(FactoryBot.build(:admin), file_type)
@@ -16,7 +18,7 @@ describe FileTypePolicy do
       end
 
       it 'does not grant access to all other users' do
-        [:external_user, :teacher].each do |factory_name|
+        %i[external_user teacher].each do |factory_name|
           expect(subject).not_to permit(FactoryBot.build(factory_name), file_type)
         end
       end
diff --git a/spec/policies/internal_user_policy_spec.rb b/spec/policies/internal_user_policy_spec.rb
index 0644e358..f4b4775a 100644
--- a/spec/policies/internal_user_policy_spec.rb
+++ b/spec/policies/internal_user_policy_spec.rb
@@ -1,13 +1,15 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe InternalUserPolicy do
   subject { described_class }
 
-  [:create?, :edit?, :index?, :new?, :show?, :update?].each do |action|
+  %i[create? edit? index? new? show? update?].each do |action|
     permissions(action) do
       it 'grants access to admins only' do
         expect(subject).to permit(FactoryBot.build(:admin), InternalUser.new)
-        [:external_user, :teacher].each do |factory_name|
+        %i[external_user teacher].each do |factory_name|
           expect(subject).not_to permit(FactoryBot.build(factory_name), InternalUser.new)
         end
       end
@@ -17,7 +19,7 @@ describe InternalUserPolicy do
   permissions :destroy? do
     context 'with an admin user' do
       it 'grants access to no one' do
-        [:admin, :external_user, :teacher].each do |factory_name|
+        %i[admin external_user teacher].each do |factory_name|
           expect(subject).not_to permit(FactoryBot.build(factory_name), FactoryBot.build(:admin))
         end
       end
@@ -26,7 +28,7 @@ describe InternalUserPolicy do
     context 'with a non-admin user' do
       it 'grants access to admins only' do
         expect(subject).to permit(FactoryBot.build(:admin), InternalUser.new)
-        [:external_user, :teacher].each do |factory_name|
+        %i[external_user teacher].each do |factory_name|
           expect(subject).not_to permit(FactoryBot.build(factory_name), FactoryBot.build(:teacher))
         end
       end
diff --git a/spec/policies/submission_policy_spec.rb b/spec/policies/submission_policy_spec.rb
index 9d79b4e1..fb1629f8 100644
--- a/spec/policies/submission_policy_spec.rb
+++ b/spec/policies/submission_policy_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe SubmissionPolicy do
@@ -5,13 +7,13 @@ describe SubmissionPolicy do
 
   permissions :create? do
     it 'grants access to anyone' do
-      [:admin, :external_user, :teacher].each do |factory_name|
+      %i[admin external_user teacher].each do |factory_name|
         expect(subject).to permit(FactoryBot.build(factory_name), Submission.new)
       end
     end
   end
 
-  [:download_file?, :render_file?, :run?, :score?, :show?, :statistics?, :stop?, :test?].each do |action|
+  %i[download_file? render_file? run? score? show? statistics? stop? test?].each do |action|
     permissions(action) do
       it 'grants access to admins' do
         expect(subject).to permit(FactoryBot.build(:admin), Submission.new)
@@ -27,7 +29,7 @@ describe SubmissionPolicy do
   permissions :index? do
     it 'grants access to admins only' do
       expect(subject).to permit(FactoryBot.build(:admin), Submission.new)
-      [:external_user, :teacher].each do |factory_name|
+      %i[external_user teacher].each do |factory_name|
         expect(subject).not_to permit(FactoryBot.build(factory_name), Submission.new)
       end
     end
diff --git a/spec/rails_helper.rb b/spec/rails_helper.rb
index e450dad2..37612d44 100644
--- a/spec/rails_helper.rb
+++ b/spec/rails_helper.rb
@@ -15,7 +15,7 @@ require 'pundit/rspec'
 # run twice. It is recommended that you do not name files matching this glob to
 # end with _spec.rb. You can configure this pattern with with the --pattern
 # option on the command line or in ~/.rspec, .rspec or `.rspec-local`.
-Dir[Rails.root.join('spec/support/**/*.rb')].sort.each { |f| require f }
+Dir[Rails.root.join('spec/support/**/*.rb')].sort.each {|f| require f }
 
 # Checks for pending migrations before tests are run.
 # If you are not using ActiveRecord, you can remove this line.
diff --git a/spec/services/proforma_service/convert_exercise_to_task_spec.rb b/spec/services/proforma_service/convert_exercise_to_task_spec.rb
index c24cdb50..e7cf793a 100644
--- a/spec/services/proforma_service/convert_exercise_to_task_spec.rb
+++ b/spec/services/proforma_service/convert_exercise_to_task_spec.rb
@@ -19,9 +19,9 @@ RSpec.describe ProformaService::ConvertExerciseToTask do
     let(:convert_to_task) { described_class.new(exercise: exercise) }
     let(:exercise) do
       FactoryBot.create(:dummy,
-                        instructions: 'instruction',
-                        uuid: SecureRandom.uuid,
-                        files: files + tests)
+        instructions: 'instruction',
+        uuid: SecureRandom.uuid,
+        files: files + tests)
     end
     let(:files) { [] }
     let(:tests) { [] }
diff --git a/spec/services/proforma_service/convert_task_to_exercise_spec.rb b/spec/services/proforma_service/convert_task_to_exercise_spec.rb
index a9f4f0e1..733775ff 100644
--- a/spec/services/proforma_service/convert_task_to_exercise_spec.rb
+++ b/spec/services/proforma_service/convert_task_to_exercise_spec.rb
@@ -3,7 +3,7 @@
 require 'rails_helper'
 
 describe ProformaService::ConvertTaskToExercise do
-  # ToDo: Add teacher_defined_linter for tests
+  # TODO: Add teacher_defined_linter for tests
 
   describe '.new' do
     subject(:convert_to_exercise_service) { described_class.new(task: task, user: user, exercise: exercise) }
@@ -232,7 +232,7 @@ describe ProformaService::ConvertTaskToExercise do
           meta_data: {
             'feedback-message' => 'feedback-message',
             'testing-framework' => 'testing-framework',
-            'testing-framework-version' => 'testing-framework-version'
+            'testing-framework-version' => 'testing-framework-version',
           }
         )
       end
@@ -252,11 +252,11 @@ describe ProformaService::ConvertTaskToExercise do
       end
 
       it 'creates an exercise with a test' do
-        expect(convert_to_exercise_service.files.select { |file| file.role == 'teacher_defined_test' }).to have(1).item
+        expect(convert_to_exercise_service.files.select {|file| file.role == 'teacher_defined_test' }).to have(1).item
       end
 
       it 'creates an exercise with a test with correct attributes' do
-        expect(convert_to_exercise_service.files.select { |file| file.role == 'teacher_defined_test' }.first).to have_attributes(
+        expect(convert_to_exercise_service.files.find {|file| file.role == 'teacher_defined_test' }).to have_attributes(
           feedback_message: 'feedback-message',
           content: 'testfile-content',
           name: 'testfile',
@@ -275,7 +275,7 @@ describe ProformaService::ConvertTaskToExercise do
             meta_data: {
               'feedback-message' => 'feedback-message',
               'testing-framework' => 'testing-framework',
-              'testing-framework-version' => 'testing-framework-version'
+              'testing-framework-version' => 'testing-framework-version',
             }
           )
         end
@@ -294,7 +294,7 @@ describe ProformaService::ConvertTaskToExercise do
         end
 
         it 'creates an exercise with two test' do
-          expect(convert_to_exercise_service.files.select { |file| file.role == 'teacher_defined_test' }).to have(2).items
+          expect(convert_to_exercise_service.files.select {|file| file.role == 'teacher_defined_test' }).to have(2).items
         end
       end
     end
@@ -355,7 +355,7 @@ describe ProformaService::ConvertTaskToExercise do
             meta_data: {
               'feedback-message' => 'feedback-message',
               'testing-framework' => 'testing-framework',
-              'testing-framework-version' => 'testing-framework-version'
+              'testing-framework-version' => 'testing-framework-version',
             }
           )
         end
diff --git a/spec/services/proforma_service/import_spec.rb b/spec/services/proforma_service/import_spec.rb
index 39c5e123..98b074cc 100644
--- a/spec/services/proforma_service/import_spec.rb
+++ b/spec/services/proforma_service/import_spec.rb
@@ -26,11 +26,11 @@ describe ProformaService::Import do
     let(:zip_file) { Tempfile.new('proforma_test_zip_file', encoding: 'ascii-8bit') }
     let(:exercise) do
       FactoryBot.create(:dummy,
-                        instructions: 'instruction',
-                        execution_environment: execution_environment,
-                        files: files + tests,
-                        uuid: uuid,
-                        user: user)
+        instructions: 'instruction',
+        execution_environment: execution_environment,
+        files: files + tests,
+        uuid: uuid,
+        user: user)
     end
 
     let(:uuid) {}
@@ -156,7 +156,7 @@ describe ProformaService::Import do
         let(:import_user) { FactoryBot.create(:teacher) }
 
         it 'raises a proforma error' do
-          expect { imported_exercise.save! } .to raise_error Proforma::ExerciseNotOwned
+          expect { imported_exercise.save! }.to raise_error Proforma::ExerciseNotOwned
         end
       end
     end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 570c271b..29f1f57a 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # This file was generated by the `rails generate rspec:install` command. Conventionally, all
 # specs live under a `spec` directory, which RSpec adds to the `$LOAD_PATH`.
 # The generated `.rspec` file contains `--require spec_helper` which will cause this
@@ -16,8 +18,8 @@
 # See http://rubydoc.info/gems/rspec-core/RSpec/Core/Configuration
 
 unless RUBY_PLATFORM == 'java'
-    require 'simplecov'
-    SimpleCov.start('rails')
+  require 'simplecov'
+  SimpleCov.start('rails')
 end
 
 require 'webmock/rspec'
diff --git a/spec/support/anonymous_controller.rb b/spec/support/anonymous_controller.rb
index ab34e749..f7b294c8 100644
--- a/spec/support/anonymous_controller.rb
+++ b/spec/support/anonymous_controller.rb
@@ -1,10 +1,11 @@
+# frozen_string_literal: true
+
 class AnonymousController < ApplicationController
   def flash
     @flash ||= {}
   end
 
-  def redirect_to(*)
-  end
+  def redirect_to(*); end
 
   def session
     @session ||= {}
diff --git a/spec/support/authentication.rb b/spec/support/authentication.rb
index 3bcf42ff..fedb57b0 100644
--- a/spec/support/authentication.rb
+++ b/spec/support/authentication.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Authentication
   def sign_in(user, password)
     page.driver.post(sessions_url, email: user.email, password: password)
diff --git a/spec/support/controllers.rb b/spec/support/controllers.rb
index 7e32344e..9246911a 100644
--- a/spec/support/controllers.rb
+++ b/spec/support/controllers.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 def expect_assigns(pairs)
   pairs.each do |key, value|
     it "assigns @#{key}" do
@@ -61,12 +63,12 @@ end
 
 def obtain_object(object)
   case object
-  when Proc
-    object.call
-  when Symbol
-    send(object)
-  else
-    object
+    when Proc
+      object.call
+    when Symbol
+      send(object)
+    else
+      object
   end
 end
 private :obtain_object
diff --git a/spec/support/database_cleaner.rb b/spec/support/database_cleaner.rb
index e283ef43..38622291 100644
--- a/spec/support/database_cleaner.rb
+++ b/spec/support/database_cleaner.rb
@@ -3,7 +3,6 @@
 require 'capybara/rspec'
 
 RSpec.configure do |config|
-
   config.use_transactional_fixtures = false
 
   config.before(:suite) do
diff --git a/spec/support/docker.rb b/spec/support/docker.rb
index 4879e92c..481fa343 100644
--- a/spec/support/docker.rb
+++ b/spec/support/docker.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 CONTAINER = Docker::Container.send(:new, Docker::Connection.new('http://example.org', {}), 'id' => SecureRandom.hex)
 IMAGE = Docker::Image.new(Docker::Connection.new('http://example.org', {}), 'id' => SecureRandom.hex, 'RepoTags' => [FactoryBot.attributes_for(:ruby)[:docker_image]])
 
@@ -16,7 +18,7 @@ RSpec.configure do |config|
 
   config.after(:suite) do
     examples = RSpec.world.filtered_examples.values.flatten
-    has_docker_tests = examples.any? { |example| example.metadata[:docker] }
+    has_docker_tests = examples.any? {|example| example.metadata[:docker] }
     next unless has_docker_tests
 
     FileUtils.rm_rf(Rails.root.join('tmp', 'files', 'test'))
diff --git a/spec/support/expectations/equal_exercise.rb b/spec/support/expectations/equal_exercise.rb
index 8f72955c..5cdaece9 100644
--- a/spec/support/expectations/equal_exercise.rb
+++ b/spec/support/expectations/equal_exercise.rb
@@ -31,7 +31,7 @@ RSpec::Matchers.define :be_an_equal_exercise_as do |exercise|
     return true if object == other # for []
     return false if object.length != other.length
 
-    object.to_a.product(other.to_a).map { |k, v| equal?(k, v) }.any?
+    object.to_a.product(other.to_a).map {|k, v| equal?(k, v) }.any?
   end
 
   def attributes_and_associations(object)
diff --git a/spec/support/factory_bot.rb b/spec/support/factory_bot.rb
index 0d06db80..891db349 100644
--- a/spec/support/factory_bot.rb
+++ b/spec/support/factory_bot.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'factory_bot'
 
 # Use "old" FactoryBot default to allow auto-creating associations for #build
diff --git a/spec/support/features.rb b/spec/support/features.rb
index 47021c3b..8430acbd 100644
--- a/spec/support/features.rb
+++ b/spec/support/features.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 def expect_forbidden_path(path_name)
   it "forbids to access the #{path_name.to_s.split('_').join(' ')}" do
     visit(send(path_name))
diff --git a/spec/support/selenium.rb b/spec/support/selenium.rb
index fd43b767..2732bf7f 100644
--- a/spec/support/selenium.rb
+++ b/spec/support/selenium.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'capybara/rspec'
 require 'selenium/webdriver'
 
diff --git a/spec/support/silencer.rb b/spec/support/silencer.rb
index 6db3fa56..511abb54 100644
--- a/spec/support/silencer.rb
+++ b/spec/support/silencer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Silencer
   def silenced
     @stdout = $stdout
diff --git a/spec/support/wait_for_ajax.rb b/spec/support/wait_for_ajax.rb
index 9a25b26c..5195e0c8 100644
--- a/spec/support/wait_for_ajax.rb
+++ b/spec/support/wait_for_ajax.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module WaitForAjax
   def wait_for_ajax
     Timeout.timeout(Capybara.default_wait_time) do
diff --git a/spec/uploaders/file_uploader_spec.rb b/spec/uploaders/file_uploader_spec.rb
index 3d335fa4..29dc2d08 100644
--- a/spec/uploaders/file_uploader_spec.rb
+++ b/spec/uploaders/file_uploader_spec.rb
@@ -1,11 +1,14 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe FileUploader do
   let(:file_path) { Rails.root.join('db', 'seeds', 'fibonacci', 'exercise.rb') }
   let(:uploader) { described_class.new(FactoryBot.create(:file)) }
 
-  before(:each) { uploader.store!(File.open(file_path, 'r')) }
-  after(:each) { uploader.remove! }
+  before { uploader.store!(File.open(file_path, 'r')) }
+
+  after { uploader.remove! }
 
   it 'uses the specified storage directory' do
     expect(uploader.file.path).to start_with(Rails.root.join('public', uploader.store_dir).to_s)
diff --git a/spec/views/execution_environments/shell.html.slim_spec.rb b/spec/views/execution_environments/shell.html.slim_spec.rb
index 84adb038..30cec4ef 100644
--- a/spec/views/execution_environments/shell.html.slim_spec.rb
+++ b/spec/views/execution_environments/shell.html.slim_spec.rb
@@ -1,9 +1,11 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe 'execution_environments/shell.html.slim' do
   let(:execution_environment) { FactoryBot.create(:ruby) }
 
-  before(:each) do
+  before do
     assign(:execution_environment, execution_environment)
     render
   end
diff --git a/spec/views/exercises/implement.html.slim_spec.rb b/spec/views/exercises/implement.html.slim_spec.rb
index 1944aa31..66d7a035 100644
--- a/spec/views/exercises/implement.html.slim_spec.rb
+++ b/spec/views/exercises/implement.html.slim_spec.rb
@@ -1,11 +1,13 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe 'exercises/implement.html.slim' do
   let(:exercise) { FactoryBot.create(:fibonacci) }
   let(:files) { exercise.files.visible }
-  let(:non_binary_files) { files.reject { |file| file.file_type.binary? } }
+  let(:non_binary_files) { files.reject {|file| file.file_type.binary? } }
 
-  before(:each) do
+  before do
     assign(:current_user, FactoryBot.create(:admin))
     assign(:exercise, exercise)
     assign(:files, files)