SessionTest : Assertion failure as a side effect of previous sessions not being closed

SessionTest test cases fail in my environment (assertion failure on sequence number not being as expected)
This looks like the consequence of previous session file store not being deleted prior to running the test case. These file store can't be deleted unless the previous session used for test has been closed.
Since the session is a Closeable, I guess it should be closed at the end of each test case: by doing so tests run successfully every time.