Major Description
ant test-core -Dtestcase=TestBackwardsCompatibility -Dtests.codec=Lucene3x
This test isnt allowed to run Lucene3x, but the assumption stuff is per-method, it still loads things up in beforeClass, meaning we checkindex() real 3.x segments with the "fake" 3.x impersonator and it looks like corruption, which is really scary if you are just trying to run all the tests with -Dtests.codec=Lucene3x to verify a change doesnt break backwards compat.