diff --git a/app/models/submission.rb b/app/models/submission.rb
index 29b803d1..267811b0 100644
--- a/app/models/submission.rb
+++ b/app/models/submission.rb
@@ -141,33 +141,7 @@ class Submission < ApplicationRecord
     # If prepared_runner raises an error, no Testrun will be created.
     prepared_runner do |runner, waiting_duration|
       file_scores = collect_files.select(&:teacher_defined_assessment?).map do |file|
-        score_command = command_for execution_environment.test_command, file.name_with_extension
-        output = {file_role: file.role, waiting_for_container_time: waiting_duration}
-        stdout = +''
-        stderr = +''
-        begin
-          exit_code = 1 # default to error
-          execution_time = runner.attach_to_execution(score_command) do |socket|
-            socket.on :stderr do |data|
-              stderr << data
-            end
-            socket.on :stdout do |data|
-              stdout << data
-            end
-            socket.on :exit do |received_exit_code|
-              exit_code = received_exit_code
-            end
-          end
-          output.merge!(container_execution_time: execution_time, status: exit_code.zero? ? :ok : :failed)
-        rescue Runner::Error::ExecutionTimeout => e
-          Rails.logger.debug { "Running tests in #{file.name_with_extension} for submission #{id} timed out: #{e.message}" }
-          output.merge!(status: :timeout, container_execution_time: e.execution_duration)
-        rescue Runner::Error => e
-          Rails.logger.debug { "Running tests in #{file.name_with_extension} for submission #{id} failed: #{e.message}" }
-          output.merge!(status: :failed, container_execution_time: e.execution_duration)
-        ensure
-          output.merge!(stdout: stdout, stderr: stderr)
-        end
+        output = run_test_file file, runner, waiting_duration
         score_file(output, file)
       end
     end
@@ -187,6 +161,36 @@ class Submission < ApplicationRecord
     durations
   end
 
+  def run_test_file(file, runner, waiting_duration)
+    score_command = command_for execution_environment.test_command, file.name_with_extension
+    output = {file_role: file.role, waiting_for_container_time: waiting_duration}
+    stdout = +''
+    stderr = +''
+    begin
+      exit_code = 1 # default to error
+      execution_time = runner.attach_to_execution(score_command) do |socket|
+        socket.on :stderr do |data|
+          stderr << data
+        end
+        socket.on :stdout do |data|
+          stdout << data
+        end
+        socket.on :exit do |received_exit_code|
+          exit_code = received_exit_code
+        end
+      end
+      output.merge!(container_execution_time: execution_time, status: exit_code.zero? ? :ok : :failed)
+    rescue Runner::Error::ExecutionTimeout => e
+      Rails.logger.debug { "Running tests in #{file.name_with_extension} for submission #{id} timed out: #{e.message}" }
+      output.merge!(status: :timeout, container_execution_time: e.execution_duration)
+    rescue Runner::Error => e
+      Rails.logger.debug { "Running tests in #{file.name_with_extension} for submission #{id} failed: #{e.message}" }
+      output.merge!(status: :failed, container_execution_time: e.execution_duration)
+    ensure
+      output.merge!(stdout: stdout, stderr: stderr)
+    end
+  end
+
   private
 
   def prepared_runner