The new robolectric version changed the behavior such that the app ID
that was returned for our app was `org.mozilla.fenix.debug` instead of
(I guess) `org.mozilla.fenix`. In general, relying on robolectric can be
fragile, such as this case, so it's better to mock. Also, this test
behavior should theoretically have varied between build flavors so
mocking prevents the tests from breaking across flavors.