Create the file empty_page.php using the following: <?php require_once('config.php'); $PAGE->set_context(context_system::instance()); $PAGE->set_url('/empty_page.php'); $PAGE->set_heading('Empty page'); $PAGE->set_pagelayout('admin'); echo $OUTPUT->header(); echo $OUTPUT->render_from_template('core/notification_problem', array('message' => 'Notification displayed')); // echo $OUTPUT->render_from_template('core/output/notification_problem', array('message' => 'Notification that should NOT be displayed')); echo $OUTPUT->footer(); Copy lib/templates/notification_problem.mustache to lib/templates/output/notification_problem.mustache Access that page, and confirm that the first notification is displayed Uncomment the notification that was commented, and comment the other one Refresh the page, and confirm that an exception is raised because the file is in a subdirectory If time allows, that'd be good to test again on a Windows server