public void Stack() {
queue.Push(1);
Assert.IsTrue(queue.Check());
queue.Push(2);
Assert.IsTrue(queue.Check());
queue.Push(3);
Assert.IsTrue(queue.Check());
Assert.AreEqual(3, queue.Pop());
Assert.IsTrue(queue.Check());
Assert.AreEqual(2, queue.Pop());
Assert.IsTrue(queue.Check());
Assert.AreEqual(1, queue.Pop());
Assert.IsTrue(queue.Check());
}