Test 1 Log in as s1 and go to Calendar. Click Manage Subscription button. Add a new subscription using this ICAL url: https://calendar.google.com/calendar/ical/en.usa%23holiday%40group.v.calendar.google.com/public/basic.ics Repeat above steps, with s2 user. Log in as admin and go to Site administration > Users > Accounts > Browse list of users. Find s1 user hover over the name link and make note of the id (should be 3 if you are using MDK). Open the database and get the event_subscriptions for the user: SELECT * FROM mdl_event_subscriptions WHERE user = YOUR_USERID; Now on the Moodle UI delete s1 user. Run the query from step 8 again and  verify there are no results. Test 2 For this test you need to create an instance based on the last weekly, in order to test upgrading. Create, but DO NOT INSTALL, a new instance of integration (master, 37, 36) Now, checkout the last weekly: master: git checkout 310d6901f9260ad 37: git checkout f3c2624fbc4 36: git checkout 2baf9a81d81 Install the site. Log in as admin. Create a new user (let's say s3), make note of the userid. Log in as that user and go to Calendar > Manage subscriptions. Add a new subscription using this ICAL url: https://calendar.google.com/calendar/ical/en.usa%23holiday%40group.v.calendar.google.com/public/basic.ics Open the database editor and delete that user manually from mdl_user table. DELETE FROM mdl_user where id = X Where X is the ID you took note. Now checkout the current head:: master: git checkout master 37: git checkout MOODLE_37_STABLE 36: git checkout MOODLE_36_STABLE Run the upgrade Look mdl_event_subscriptions table and make sure there are no subscriptions for that user ID. SELECT * FROM mdl_event_subscriptions where userid = X