diff --git a/spec/lib/runner/strategy/docker_container_pool_spec.rb b/spec/lib/runner/strategy/docker_container_pool_spec.rb
index 67c9b20f..d5c5a455 100644
--- a/spec/lib/runner/strategy/docker_container_pool_spec.rb
+++ b/spec/lib/runner/strategy/docker_container_pool_spec.rb
@@ -1,15 +1,278 @@
 # frozen_string_literal: true
 
 require 'rails_helper'
+require 'pathname'
 
 describe Runner::Strategy::DockerContainerPool do
   let(:runner_id) { FactoryBot.attributes_for(:runner)[:runner_id] }
   let(:execution_environment) { FactoryBot.create :ruby }
   let(:container_pool) { described_class.new(runner_id, execution_environment) }
+  let(:docker_container_pool_url) { 'http://localhost:1234' }
+  let(:config) { {pool: {location: docker_container_pool_url}} }
+  let(:container) { instance_double(Docker::Container) }
 
-  # TODO: add tests for these methods when implemented
-  it 'defines all methods all runner management strategies must define' do
-    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)
+  before do
+    allow(described_class).to receive(:config).and_return(config)
+    allow(container).to receive(:id).and_return(runner_id)
+  end
+
+  # All requests handle a Faraday error the same way.
+  shared_examples 'Faraday error handling' do
+    it 'raises a runner error' do
+      allow(Faraday).to receive(:get).and_raise(Faraday::TimeoutError)
+      expect { action.call }.to raise_error(Runner::Error::Unknown, /Faraday/)
+    end
+  end
+
+  describe '::request_from_management' do
+    let(:action) { -> { described_class.request_from_management(execution_environment) } }
+    let(:response_body) { nil }
+    let!(:request_runner_stub) do
+      WebMock
+        .stub_request(:get, "#{docker_container_pool_url}/docker_container_pool/get_container/#{execution_environment.id}")
+        .to_return(body: response_body, status: 200)
+    end
+
+    context 'when the DockerContainerPool returns an id' do
+      let(:response_body) { {id: runner_id}.to_json }
+
+      it 'successfully requests the DockerContainerPool' do
+        action.call
+        expect(request_runner_stub).to have_been_requested.once
+      end
+
+      it 'returns the received runner id' do
+        id = action.call
+        expect(id).to eq(runner_id)
+      end
+    end
+
+    context 'when the DockerContainerPool does not return an id' do
+      let(:response_body) { {}.to_json }
+
+      it 'raises an error' do
+        expect { action.call }.to raise_error(Runner::Error::NotAvailable)
+      end
+    end
+
+    context 'when the DockerContainerPool returns invalid JSON' do
+      let(:response_body) { '{hello}' }
+
+      it 'raises an error' do
+        expect { action.call }.to raise_error(Runner::Error::Unknown)
+      end
+    end
+
+    include_examples 'Faraday error handling'
+  end
+
+  describe '#destroy_at_management' do
+    let(:action) { -> { container_pool.destroy_at_management } }
+    let!(:destroy_runner_stub) do
+      WebMock
+        .stub_request(:get, "#{docker_container_pool_url}/docker_container_pool/destroy_container/#{runner_id}")
+        .to_return(body: nil, status: 200)
+    end
+
+    before { allow(container_pool).to receive(:container).and_return(container) }
+
+    it 'successfully requests the DockerContainerPool' do
+      action.call
+      expect(destroy_runner_stub).to have_been_requested.once
+    end
+
+    include_examples 'Faraday error handling'
+  end
+
+  describe '#copy_files' do
+    let(:files) { [] }
+    let(:action) { -> { container_pool.copy_files(files) } }
+    let(:local_path) { Pathname.new('/tmp/container20') }
+
+    before do
+      allow(container_pool).to receive(:local_workspace_path).and_return(local_path)
+      allow(container_pool).to receive(:clean_workspace)
+      allow(FileUtils).to receive(:chmod_R)
+    end
+
+    it 'creates the workspace directory' do
+      expect(FileUtils).to receive(:mkdir_p).with(local_path)
+      container_pool.copy_files(files)
+    end
+
+    it 'cleans the workspace' do
+      expect(container_pool).to receive(:clean_workspace)
+      container_pool.copy_files(files)
+    end
+
+    it 'sets permission bits on the workspace' do
+      expect(FileUtils).to receive(:chmod_R).with('+rwX', local_path)
+      container_pool.copy_files(files)
+    end
+
+    context 'when receiving a normal file' do
+      let(:file_content) { 'print("Hello World!")' }
+      let(:files) { [FactoryBot.build(:file, content: file_content)] }
+
+      it 'writes the file to disk' do
+        file = instance_double(File)
+        allow(File).to receive(:open).and_yield(file)
+        expect(file).to receive(:write).with(file_content)
+        container_pool.copy_files(files)
+      end
+
+      it 'creates the file inside the workspace' do
+        expect(File).to receive(:open).with(local_path.join(files.first.filepath), 'w')
+        container_pool.copy_files(files)
+      end
+
+      it 'raises an error in case of an IOError' do
+        allow(File).to receive(:open).and_raise(IOError)
+        expect { container_pool.copy_files(files) }.to raise_error(Runner::Error::Unknown, /#{files.first.filepath}/)
+      end
+
+      it 'does not create a directory for it' do
+        expect(FileUtils).not_to receive(:mkdir_p)
+      end
+
+      context 'when the file is inside a directory' do
+        let(:directory) { 'temp/dir' }
+        let(:files) { [FactoryBot.build(:file, path: directory)] }
+
+        before do
+          allow(File).to receive(:open)
+          allow(FileUtils).to receive(:mkdir_p).with(local_path)
+          allow(FileUtils).to receive(:mkdir_p).with(local_path.join(directory))
+        end
+
+        it 'cleans the directory path' do
+          allow(container_pool).to receive(:local_path).and_call_original
+          expect(container_pool).to receive(:local_path).with(directory).and_call_original
+          container_pool.copy_files(files)
+        end
+
+        it 'creates the directory of the file' do
+          expect(FileUtils).to receive(:mkdir_p).with(local_path.join(directory))
+          container_pool.copy_files(files)
+        end
+      end
+    end
+
+    context 'when receiving a binary file' do
+      let(:files) { [FactoryBot.build(:file, :image)] }
+
+      it 'copies the file inside the workspace' do
+        expect(FileUtils).to receive(:cp).with(files.first.native_file.path, local_path.join(files.first.filepath))
+        container_pool.copy_files(files)
+      end
+    end
+
+    context 'when receiving multiple files' do
+      let(:files) { FactoryBot.build_list(:file, 3) }
+
+      it 'creates all files' do
+        files.each do |file|
+          expect(File).to receive(:open).with(local_path.join(file.filepath), 'w')
+        end
+        container_pool.copy_files(files)
+      end
+    end
+  end
+
+  describe '#local_workspace_path' do
+    before { allow(container_pool).to receive(:container).and_return(container) }
+
+    it 'returns the local part of the mount binding' do
+      local_path = 'tmp/container20'
+      allow(container).to receive(:binds).and_return(["#{local_path}:/workspace"])
+      expect(container_pool.send(:local_workspace_path)).to eq(Pathname.new(local_path))
+    end
+  end
+
+  describe '#local_path' do
+    let(:local_workspace) { Pathname.new('/tmp/workspace') }
+
+    before { allow(container_pool).to receive(:local_workspace_path).and_return(local_workspace) }
+
+    it 'raises an error for relative paths outside of the workspace' do
+      expect { container_pool.send(:local_path, '../exercise.py') }.to raise_error(Runner::Error::Unknown, %r{tmp/exercise.py})
+    end
+
+    it 'raises an error for absolute paths outside of the workspace' do
+      expect { container_pool.send(:local_path, '/test') }.to raise_error(Runner::Error::Unknown, %r{/test})
+    end
+
+    it 'removes .. from the path' do
+      expect(container_pool.send(:local_path, 'test/../exercise.py')).to eq(Pathname.new('/tmp/workspace/exercise.py'))
+    end
+
+    it 'joins the given path with the local workspace path' do
+      expect(container_pool.send(:local_path, 'exercise.py')).to eq(Pathname.new('/tmp/workspace/exercise.py'))
+    end
+  end
+
+  describe '#clean_workspace' do
+    let(:local_workspace) { instance_double(Pathname) }
+
+    before { allow(container_pool).to receive(:local_workspace_path).and_return(local_workspace) }
+
+    it 'removes all children of the workspace recursively' do
+      children = %w[test.py exercise.rb subfolder].map {|child| Pathname.new(child) }
+      allow(local_workspace).to receive(:children).and_return(children)
+      expect(FileUtils).to receive(:rm_r).with(children, secure: true)
+      container_pool.send(:clean_workspace)
+    end
+
+    it 'raises an error if the workspace does not exist' do
+      allow(local_workspace).to receive(:children).and_raise(Errno::ENOENT)
+      expect { container_pool.send(:clean_workspace) }.to raise_error(Runner::Error::Unknown, /not exist/)
+    end
+
+    it 'raises an error if it lacks permission for deleting an entry' do
+      allow(local_workspace).to receive(:children).and_return(['test.py'])
+      allow(FileUtils).to receive(:remove_entry_secure).and_raise(Errno::EACCES)
+      expect { container_pool.send(:clean_workspace) }.to raise_error(Runner::Error::Unknown, /Not allowed/)
+    end
+  end
+
+  describe '#container' do
+    it 'raises an error if there is no container for the saved id' do
+      allow(Docker::Container).to receive(:get).and_raise(Docker::Error::NotFoundError)
+      expect { container_pool.send(:container) }.to raise_error(Runner::Error::RunnerNotFound)
+    end
+
+    it 'raises an error if the received container is not running' do
+      allow(Docker::Container).to receive(:get).and_return(container)
+      allow(container).to receive(:info).and_return({'State' => {'Running' => false}})
+      expect { container_pool.send(:container) }.to raise_error(Runner::Error::RunnerNotFound)
+    end
+
+    it 'returns the received container' do
+      allow(Docker::Container).to receive(:get).and_return(container)
+      allow(container).to receive(:info).and_return({'State' => {'Running' => true}})
+      expect(container_pool.send(:container)).to eq(container)
+    end
+
+    it 'does not request a container if one is saved' do
+      container_pool.instance_variable_set(:@container, container)
+      expect(Docker::Container).not_to receive(:get)
+      container_pool.send(:container)
+    end
+  end
+
+  describe '#attach_to_execution' do
+    # TODO: add more tests here
+
+    let(:command) { 'ls' }
+    let(:action) { -> { container_pool.attach_to_execution(command) } }
+    let(:websocket_url) { 'ws://ws.example.com/path/to/websocket' }
+
+    it 'returns the execution time' do
+      allow(EventMachine).to receive(:run)
+      starting_time = Time.zone.now
+      execution_time = action.call
+      test_time = Time.zone.now - starting_time
+      expect(execution_time).to be_between(0.0, test_time).exclusive
+    end
   end
 end
diff --git a/spec/lib/runner/strategy/poseidon_spec.rb b/spec/lib/runner/strategy/poseidon_spec.rb
index 62bbd638..add7037e 100644
--- a/spec/lib/runner/strategy/poseidon_spec.rb
+++ b/spec/lib/runner/strategy/poseidon_spec.rb
@@ -292,7 +292,7 @@ describe Runner::Strategy::Poseidon do
     # TODO: add more tests here
 
     let(:command) { 'ls' }
-    let(:action) { -> { poseidon.attach_to_execution command } }
+    let(:action) { -> { poseidon.attach_to_execution(command) } }
     let(:websocket_url) { 'ws://ws.example.com/path/to/websocket' }
 
     it 'returns the execution time' do
@@ -302,7 +302,7 @@ describe Runner::Strategy::Poseidon do
       starting_time = Time.zone.now
       execution_time = action.call
       test_time = Time.zone.now - starting_time
-      expect(execution_time).to be_between(0.0, test_time)
+      expect(execution_time).to be_between(0.0, test_time).exclusive
     end
   end
 end
diff --git a/spec/models/runner_spec.rb b/spec/models/runner_spec.rb
index b9395645..771f2b4d 100644
--- a/spec/models/runner_spec.rb
+++ b/spec/models/runner_spec.rb
@@ -98,7 +98,8 @@ describe Runner do
         runner.copy_files(nil)
       end
 
-      it 'retries to copy the files' do
+      it 'calls copy_file twice' do
+        # copy_files is called again after a new runner was requested.
         expect(strategy).to receive(:copy_files).twice
         runner.copy_files(nil)
       end