As teacher, create a quiz and set a time limit and set When time expires to Allow a grace period to submit, but not change any responses or set an End Date. Set Submission grace period to a suitable amount of time to let you do the tests below.
1. As a student, start a quiz attempt and answer some questions. Then log out of Moodle. The quiz cron has not run yet.
2. Wait until the time limit of the quiz has expired.
3. The quiz cron runs.
4. Log in as teacher, and you will be able to see that the attempt has been updated to be Overdue.
5. Login as a student and click the Continue last attempt button and you will be taken to the summary page, where you are told you can still submit up to a certain time.
6. Do not submit the attempt before the grace period expires. Then refresh the page and check that the attempt is set to "Never submitted".
7. Log in as teacher and check that the quiz attempt is set to "Never submitted".