}
    }
  }

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

  private void checkZeroElements(BlockingQueue<Object> q) throws InterruptedException {
    for (boolean interruptibly : new boolean[] {true, false}) {
      // asking to drain zero elements