It turns out that Mockito isn't needed, since MockObjectFactory was only being used by TestLargeObjectLoader, and then only to configure the output committer. I've simplified the test so that it doesn't use an output committer (since that isn't a part of the behaviour being tested), and now MockObjectFactory is no longer needed.
Also, HadoopTestCase wasn't really being used, so I've removed that dependency too. The tests that I've changed work on both 0.20 and 0.23, so I think this change can be committed. Please review.
Having a switch to build on either 0.20 or 0.23 should be tackled in another issue.