Behat and unit tests provided Prerequisites: Create a course with a student and teacher enrolled. Create a forum activity in the course. Create 2 discussions named Discussion1 and Discussion2 For both discussions, post a reply.  Manual testing: Case 1 Login as a teacher For both discussions created, confirm you can see the 'Lock' link With Discussion1, confirm on click of the 'Lock' link, it reloads the page and the link changes to 'Locked' Confirm you can see the following message: ' This discussion has been locked so you can no longer reply to it.' With Discussion2, confirm you do not see the message in #4. Login as a student and go to the course and forum activity. In Discussion1, confirm Step #4 Confirm you cannot reply to any of the posts Repeat Step #5 Confirm , you can reply to any of the posts in the discussion. Case 2 (requires 2 browsers) In browser 1, login as a teacher Goto Discussion1 and set/reset the state to 'Unlocked' In browser 2, login as a student Goto Discussion1 As the teacher, lock the discussion As the student, click on the reply button Confirm you get thrown an exception stating " Sorry, you are not allowed to post to this forum " In the "In line reply", click on "Advanced". confirm you are redirected to the same page and you see the following message 'T_his discussion has been locked so you can no longer reply to it.'_' Case 3 - Time locked discussions As a teacher, create another forum. Under " Discussion locking ", set " Lock discussions after period of inactivity " to 1 day. Create a discussion. Open your favourite DB browser (e.g. phppgadmin) and find the discussion that you created in the " mdl_forum_discussions " table. Edit the value for the " timemodified " field of that discussion to an earlier date (e.g. 1555718400, which is equivalent to 20 April 2019) Refresh the discussion page. Confirm that you see the notification message that the discussion has been locked. Confirm that you don't see the icon and link to manually lock/unlock the discussion.