yes, this is an tricky one. the pressents of this sleepSeconds() call makes no diffrence to the test.  from what I can see it only serves to give some time for the other thread to block on the call to txnQueue1.poll(),  which is not ganteried.  what is needed hear is a signal that txnQueue1.poll(...)  is called and blocked, then we do the clinentQueue.offer(..), and then check is the txnQueue returns from its call.