assertEquals("", queue.peek());
  }

  public void testPutNoInterrupt() {
    TimedPutQueue queue = TimedPutQueue.createWithDelay(20);
    queue.putSuccessfully();
    assertNotInterrupted();
  }

  public void testPutSingleInterrupt() {
    TimedPutQueue queue = TimedPutQueue.createWithDelay(50);
    requestInterruptIn(10);
    queue.putSuccessfully();
    assertInterrupted();
  }