The bug is not triggered by the coursecat PHPUnit test because the test indirectly includes the course/lib.php via the testing_data_generator->create_course() method. Create a new course category Create a course within this category Create a PHP script (coursecat_delete_move.php) inside the Moodle root directory with the following content: <?php require_once( 'config.php' ); require_once($CFG->libdir . '/coursecatlib.php' ); $coursecatid = required_param( 'coursecatid' , PARAM_INT); $moveto = required_param( 'moveto' , PARAM_INT); $coursecat = coursecat::get($coursecatid); $coursecat->delete_move($moveto); Run the script either from CLI or open in a browser Expected: The course category should be deleted and the course should be moved to the given category Actually: An error message is displayed: "Call to undefined function move_courses()" With the patch applied the expected behaviour should actually happen