All these "PostingsFormat" tests wire their codec to themselves. This allows us to implement generic base classes with tests that all codecs should pass, as well as codec-specific tests (e.g. in lucene41) that test particular corner cases of importance.
this worked well in knocking out bugs for postings, so the whole scheme was duplicated to docvalues, storedfields, vectors, everything.
Now here comes this commit, and these tests (which are important to ensure the index format is working) are no longer testing what they are supposed to. For example the tests in Lucene41 package explicitly test special cases of that codec that would otherwise be extraordinarily rare in the existing random tests. If they are executing against random codecs or even random configurations then they just became useless.
So thats why I'm concerned: I see this commit causing these failures, and I know we just experienced a significant loss of test coverage to the index format. We are relying upon tests to fail to detect this, but unfortunately 'loss of test coverage' doesn't always trigger a jenkins build.
So maybe instead of playing whack-a-mole with jenkins tests failures, we should pay more attention reviewing all changes to unit tests where clone() was previously used. The patch is buggy here, and I just want to ensure its taken seriously so that we do not lose coverage