Testing difficulty: Hard (requires fake web service response) To test this, the tester would need to invoke sending available updates notification via messaging API and have the admin's messaging set to receive such messages to email. It is doable via $CFG->alternativeupdateproviderurl pointing to a local script that returns fake update data. I have this set up at my machine and I already tested it. I'm not sure if putting down all the instructions to prepare such an environment are worth of testing this trivial string change.