Before patch is applied Create a course with an idnumber. Create another course with a different idnumber. Edit the second course and change the idnumber to the idnumber for the first course (there is only a check on duplicate idnumbers when creating a course, not updating). After patch is applied Test 1. Web interface Go to the settings for one of the courses you created prior to testing and do not edit anything and save, ensure it saves without an idnumber warning (even though the courses share the same idnumber). Create course with filled shortname and idnumber Attempt to create another course with the same shortname, make sure the nice descriptive error message appears Attempt to create another course with the same idnumber, make sure the nice descriptive error message appears Create another course with different shortname and empty/different idnumber Attempt to update the second course and set the same shortname as in the first course, make sure the nice descriptive error message appears Attempt to update the second course and set the same idnumber as in the first course, make sure the nice descriptive error message appears Edit some other fields and save the changes, make sure there are no errors Edit second course and try to change shortname to unused one, make sure it is updated ok Edit second course and try to change idnumber to unused one, make sure it is updated ok Revoke from teacher capability to change course shortname Login as teacher and edit any other fields in the course, make sure everything is edited ok and without warnings. Repeat for user without capability to change course idnumber Test 2. Webservices (2.5 and master only) Create and update course using webservices, make sure you can not create or update course with the same shortname or idnumber as another existing course (basically repeat test 1 but using webservices)