public void Dequeue_PassStacka_Returnsa()
        {
            TwoStackQueue2 s = new TwoStackQueue2();

            s.Enqueue("a");

            Assert.AreEqual("a", s.Dequeue());
        }
        public void Dequeue_EmptyStack_ThrowsException()
        {
            Exception exception = null;

            try
            {
                TwoStackQueue2 s = new TwoStackQueue2();
                s.Dequeue();
            }
            catch (Exception ex)
            {
                exception = ex;
            }
            Assert.IsNotNull(exception);
        }