producer.doneProducing.await();
      if (drained == 0) {
        q.poll(); // not necessarily there if producer was interrupted
      }
    }
  }

  public void testZeroElements() throws Exception {
    for (BlockingQueue<Object> q : blockingQueues()) {
      checkZeroElements(q);
    }
  }

  private void checkZeroElements(BlockingQueue<Object> q) throws InterruptedException {