The old WikibaseRepoTest and WikibaseClientTest classes override some MediaWiki services to ensure that the service setup never makes database or HTTP accesses (T243729). We should have something similar in the new unit tests for service wiring.
- WikibaseRepo https://gerrit.wikimedia.org/r/667230, https://gerrit.wikimedia.org/r/c/667890
- WikibaseClient https://gerrit.wikimedia.org/r/c/667840