SoftIndexFileStoreFunctionalTest (and others with the same pattern) uses a new (differently named) cache for each test function, assuming each is created empty. However, it reuses the same persistence tmp directory for every test and doesn't clear it between test functions. Thus a new cache can load stale persistent state from a previous test, causing intermittent failures. Perhaps use the cache name in the tmp dir path, or delete the shared dir every time, though that assumes nothing is holding an open handle on it.