Add strategy for DockerContainerPool

In order to provide an alternative to Poseidon, a strategy for the
DockerContainerPool is added that is used by the runner model.

Co-authored-by: Sebastian Serth <Sebastian.Serth@hpi.de>

spec/lib/runner/strategy/docker_container_pool_spec.rb

@@ -2,14 +2,14 @@
 
 require 'rails_helper'
 
-describe Runner::Strategy::Docker do
+describe Runner::Strategy::DockerContainerPool do
   let(:runner_id) { FactoryBot.attributes_for(:runner)[:runner_id] }
   let(:execution_environment) { FactoryBot.create :ruby }
-  let(:docker) { described_class.new(runner_id, execution_environment) }
+  let(:container_pool) { described_class.new(runner_id, execution_environment) }
 
   # TODO: add tests for these methods when implemented
   it 'defines all methods all runner management strategies must define' do
-    expect(docker.public_methods).to include(*Runner::DELEGATED_STRATEGY_METHODS)
+    expect(container_pool.public_methods).to include(:destroy_at_management, :copy_files, :attach_to_execution)
     expect(described_class.public_methods).to include(:request_from_management)
   end
 end

spec/lib/runner/strategy/poseidon_spec.rb

@@ -256,15 +256,15 @@ describe Runner::Strategy::Poseidon do
   end
 
   describe '#copy_files' do
-    let(:filename) { 'main.py' }
     let(:file_content) { 'print("Hello World!")' }
-    let(:action) { -> { poseidon.copy_files({filename => file_content}) } }
-    let(:encoded_file_content) { Base64.strict_encode64(file_content) }
+    let(:file) { FactoryBot.build(:file, content: file_content) }
+    let(:action) { -> { poseidon.copy_files([file]) } }
+    let(:encoded_file_content) { Base64.strict_encode64(file.content) }
     let!(:copy_files_stub) do
       WebMock
         .stub_request(:patch, "#{Runner::BASE_URL}/runners/#{runner_id}/files")
         .with(
-          body: {copy: [{path: filename, content: encoded_file_content}]},
+          body: {copy: [{path: file.filepath, content: encoded_file_content}]},
           headers: {'Content-Type' => 'application/json'}
         )
         .to_return(body: response_body, status: response_status)