73224f4f8b8a26b9a9a04e338bb1c3c2f163a820 changed User::addGroup to throw an exception if a group is added to a User object which is not stored in the database. Before that such calls succeeded without any DB change and while it's unclear if this was intentional (c95ec8d74e78599f26aaf70cc095bfcc29f49591 says "as paranoia, don't insert a groups record into the database if User::addGroup() ends up run on a non-existing user" so it's not exactly encouraged behavior), some tests did rely on it.
BetaFeatures tests, specifically, are failing:
23:10:44 1) AutoEnrollmentTest::testAutoEnroll with data set #0 (null, null, 'unittest-ft1', null, 'Hooks set the preference thou...t set.') 23:10:44 UnexpectedValueException: UserGroupMembership::insert() needs a positive user ID. Did you forget to add your User object to the database before calling addGroup()? 23:10:44 23:10:44 /srv/jenkins-workspace/workspace/mwext-testextension-php55/src/includes/user/UserGroupMembership.php:196 23:10:44 /srv/jenkins-workspace/workspace/mwext-testextension-php55/src/includes/user/User.php:3395 23:10:44 /srv/jenkins-workspace/workspace/mwext-testextension-php55/src/extensions/BetaFeatures/tests/phpunit/BetaFeaturesTestCase.php:39 23:10:44 /srv/jenkins-workspace/workspace/mwext-testextension-php55/src/extensions/BetaFeatures/tests/phpunit/AutoEnrollmentTest.php:144 23:10:44 /srv/jenkins-workspace/workspace/mwext-testextension-php55/src/tests/phpunit/MediaWikiTestCase.php:400 23:10:44 /srv/jenkins-workspace/workspace/mwext-testextension-php55/src/maintenance/doMaintenance.php:111 23:10:44 23:10:44 2) AutoEnrollmentTest::testAutoEnroll with data set #1 ('betafeatures-auto-enroll', '1', 'unittest-ft1', '1', 'Hooks did not set the prefere...s set.') 23:10:44 UnexpectedValueException: UserGroupMembership::insert() needs a positive user ID. Did you forget to add your User object to the database before calling addGroup()? 23:10:44 23:10:44 /srv/jenkins-workspace/workspace/mwex