tx.begin();
a = (TestClassA) _conn.getObjectByIdentity(oid);
assertTrue(a.getB() != null);
assertTrue(a.getB().getValue1().equals("value2"));
a.setB(null);
tx.commit();
tx = _kit.getTransaction(_conn);
tx.begin();
a = (TestClassA) _conn.getObjectByIdentity(oid);
assertTrue(a.getB() == null);