I suspect that CI is not running this test, because it has been failing on master for a while. I had to make these changes to successfully run the tests:
https://gerrit.wikimedia.org/r/#/c/59804/9/tests/TestsAutoLoader.php
Version: wmf-deployment
Severity: normal
The AutoLoaderTest.php is not registered in phpunit. I have created https://gerrit.wikimedia.org/r/#/c/64788/ which registered it in suite.xml under the 'structure' test suite and that fails accordingly.
Related URL: https://gerrit.wikimedia.org/r/64791 (Gerrit Change I285fa7ed24a6fc45a4dc475b54d80cf3816436fb)
https://gerrit.wikimedia.org/r/#/c/64791/ fix the missing AutoLoader entries
https://gerrit.wikimedia.org/r/#/c/64788/ move the AutoLoaderTest.php StructureTest.php files under /tests/phpunit/structures and register that directory in PHPUnit suite.
Both changes fix the issue. The later probably need a backport in release branches with their own autoloading fixes.
We should test it out one last time to make sure it is working properly.
Ideally I would want that to be backported in the release branches as well, though we usually do not introduce new classes in release branches post release.