Some PluggableAuth extension unit tests fail because tests change database content, but the test classes are not in the Database group. Becuase no database prefix is set for such tests, the tests fail with an assertion (error message: "RuntimeException: Can't create user on real database").
Todo: add classes MapGroupsTest and SyncAllGroupsTest to the Database group
See also some related links:
https://www.mediawiki.org/w/index.php?title=Topic:Xredg9711t0eje1m
https://gerrit.wikimedia.org/r/c/mediawiki/extensions/OpenIDConnect/+/965852