Ok, I've reproduced that test failure, and I think I've fixed it. Patch attached, rb: https://reviews.apache.org/r/18915/
The failure was due to state leakage between the two tests in the TestTopicMetadataCache class. They would pass if executed in the order they appear in the file, and fail if executed in the reverse order. Java 7 must have changed something about the order of methods returned by reflection APIs. I've fixed the tests to not leak state, so they should execute fine in any order.
I've also replaced the use of "assert" with "assertEquals", in order to get better error messages on test failure.