This issue is mostly self-tested by CI, however the following step must be carried out too: Apply the attached behat feature to lib/tests/behat Run behat with tags @mdl59773 Confirm that the test passed Open lib/sessionlib.php and find the cron_setup_user function. Add a call to throw new \moodle_exception('You broke it!'); Run behat with tags @mdl59773 Confirm that the test failed Confirm that a clear stacktrace was present (example below) Remove the exception and replace it with a call to trigger_error("I made a whoopsy!", E_USER_ERROR); Run behat with tags @mdl59773 Confirm that a clear stacktrace was present (example below) Note: The exception line is shown twice for triggered errors