q.poll(); // not necessarily there if producer was interrupted
      }
    }
  }

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

  private void testZeroElements(BlockingQueue<Object> q) throws InterruptedException {
    for (boolean interruptibly : new boolean[] {true, false}) {