[ticket/12341] Add tests for get_username_string()

PHPBB3-12341
Merge branch 'ticket/12341' into ticket/12341-ascraeus
[ticket/12341] Update test with new class name and dependencies

PHPBB3-12341
Merge remote-tracking branch 'Elsensee/ticket/12341' into develop-olympus

* Elsensee/ticket/12341:
  [ticket/12341] Add tests for get_username_string()
Merge remote-tracking branch 'Elsensee/ticket/12341-ascraeus' into develop-ascraeus

* Elsensee/ticket/12341-ascraeus:
  [ticket/12341] Update test with new class name and dependencies
  [ticket/12341] Add tests for get_username_string()
Merge branch 'develop-olympus' into develop-ascraeus

* develop-olympus: