Queueing the task in response to a quiz attempt is covered by the new attempt_deleted_test class. The actual calculation performed by the task is already covered in statistics_bulk_loader_test. Note, for Moodle 4.1, omit the `--classname="\quiz_statistics\task\recalculate"` argument for the CLI script. Create a quiz, on a course with at least 2 students. From the CLI, run `php admin/cli/adhoc_task.php --execute --classname="\quiz_statistics\task\recalculate"` to run any queued recalculation tasks. You should see "Ran 0 adhoc tasks" and no output from the recalculate task. Log in as each student, start and finish 2 attempts of the quiz for each student. Wait 1 hour or run `UPDATE mdl_task_adhoc SET nextruntime = 0` on your database. From the CLI, run `php admin/cli/adhoc_task.php --execute --classname="\quiz_statistics\task\recalculate"` again. You should see "Re-calculating statistics for quiz {quizname} ({quizid}) from course {shortname} ({courseid}) with 4 attempts". You should see "Ran 1 adhoc tasks". Log in as a teacher, go to the quiz, click on the "Results" tab. Scroll down to the table of attempts. Select the checkbox next to 1 attempt for each student. Click "Delete selected attempts" and confirm. Wait 1 hour or run `UPDATE mdl_task_adhoc SET nextruntime = 0` on your database. From the CLI, run `php admin/cli/adhoc_task.php --execute --classname="\quiz_statistics\task\recalculate"` again. Confirm you see "Re-calculating statistics for quiz {quizname} ({quizid}) from course {shortname} ({courseid}) with 2 attempts". Confirm you see "Ran 1 adhoc tasks". Before fix: the task was not triggered by the attempt deletion.