diff --git a/app/controllers/concerns/submission_scoring.rb b/app/controllers/concerns/submission_scoring.rb
index b1fe2daf..ea20a483 100644
--- a/app/controllers/concerns/submission_scoring.rb
+++ b/app/controllers/concerns/submission_scoring.rb
@@ -1,17 +1,30 @@
+require 'concurrent/future'
+
 module SubmissionScoring
-  def execute_test_files(submission)
+  def collect_test_results(submission)
     submission.collect_files.select(&:teacher_defined_test?).map do |file|
-      output = @docker_client.execute_test_command(submission, file.name_with_extension)
-      output.merge!(@assessor.assess(output))
-      output.merge!(filename: file.name_with_extension, message: output[:score] == Assessor::MAXIMUM_SCORE ? I18n.t('exercises.implement.default_feedback') : file.feedback_message, weight: file.weight)
+      future = Concurrent::Future.execute do
+        assessor = Assessor.new(execution_environment: submission.execution_environment)
+        output = execute_test_file(file, submission)
+        output.merge!(assessor.assess(output))
+        output.merge!(filename: file.name_with_extension, message: feedback_message(file, output[:score]), weight: file.weight)
+      end
+      future.value
     end
   end
-  private :execute_test_files
+  private :collect_test_results
+
+  def execute_test_file(file, submission)
+    DockerClient.new(execution_environment: file.context.execution_environment, user: current_user).execute_test_command(submission, file.name_with_extension)
+  end
+  private :execute_test_file
+
+  def feedback_message(file, score)
+    score == Assessor::MAXIMUM_SCORE ? I18n.t('exercises.implement.default_feedback') : file.feedback_message
+  end
 
   def score_submission(submission)
-    @assessor = Assessor.new(execution_environment: submission.execution_environment)
-    @docker_client = DockerClient.new(execution_environment: submission.execution_environment, user: current_user)
-    outputs = execute_test_files(submission)
+    outputs = collect_test_results(submission)
     score = outputs.map { |output| output[:score] * output[:weight] }.reduce(:+)
     submission.update(score: score)
     outputs
diff --git a/spec/concerns/submission_scoring_spec.rb b/spec/concerns/submission_scoring_spec.rb
index e4bf53c0..1b42a947 100644
--- a/spec/concerns/submission_scoring_spec.rb
+++ b/spec/concerns/submission_scoring_spec.rb
@@ -5,35 +5,29 @@ class Controller < AnonymousController
 end
 
 describe SubmissionScoring do
-  before(:all) do
-    @submission = FactoryGirl.create(:submission, cause: 'submit')
-  end
-
   let(:controller) { Controller.new }
+  before(:all) { @submission = FactoryGirl.create(:submission, cause: 'submit') }
   before(:each) { controller.instance_variable_set(:@current_user, FactoryGirl.create(:external_user)) }
 
-  describe '#score_submission' do
-    let(:score_submission) { proc { controller.score_submission(@submission) } }
-    before(:each) { score_submission.call }
+  describe '#collect_test_results' do
+    after(:each) { controller.send(:collect_test_results, @submission) }
 
-    it 'assigns @assessor' do
-      expect(controller.instance_variable_get(:@assessor)).to be_an(Assessor)
-    end
-
-    it 'assigns @docker_client' do
-      expect(controller.instance_variable_get(:@docker_client)).to be_a(DockerClient)
-    end
-
-    it 'executes the teacher-defined test cases' do
+    it 'executes every teacher-defined test file' do
       @submission.collect_files.select(&:teacher_defined_test?).each do |file|
-        expect_any_instance_of(DockerClient).to receive(:execute_test_command).with(@submission, file.name_with_extension).and_return({})
+        expect(controller).to receive(:execute_test_file).with(file, @submission).and_return({})
       end
-      score_submission.call
+    end
+  end
+
+  describe '#score_submission' do
+    after(:each) { controller.score_submission(@submission) }
+
+    it 'collects the test results' do
+      expect(controller).to receive(:collect_test_results).and_return([])
     end
 
-    it 'updates the submission' do
+    it 'assigns a score to the submissions' do
       expect(@submission).to receive(:update).with(score: anything)
-      score_submission.call
     end
   end
 end
diff --git a/spec/controllers/exercises_controller_spec.rb b/spec/controllers/exercises_controller_spec.rb
index 34d286dd..b2cfb569 100644
--- a/spec/controllers/exercises_controller_spec.rb
+++ b/spec/controllers/exercises_controller_spec.rb
@@ -210,7 +210,7 @@ describe ExercisesController do
 
     before(:each) do
       allow_any_instance_of(Submission).to receive(:normalized_score).and_return(1)
-      expect(controller).to receive(:execute_test_files).and_return([{score: 1, weight: 1}])
+      expect(controller).to receive(:collect_test_results).and_return([{score: 1, weight: 1}])
       expect(controller).to receive(:score_submission).and_call_original
     end