public void ShouldCleanEmptyStack()
        {
            CalculatorContainer container = new CalculatorContainer();

            container.PushItem(5);
            container.PushItem(5);
            Assert.That(container.Count() > 0);
            container.Clean();
            Assert.That(container.Count() == 0);
        }
        public void ShouldCoutStack()
        {
            CalculatorContainer container = new CalculatorContainer();

            Assert.AreEqual(0, container.Count());
            container.PushItem(5);
            container.PushItem(7);
            Assert.AreEqual(2, container.Count());
            container.PushItem(19);
            Assert.AreEqual(3, container.Count());
        }
        public void ShouldPushItemToStack()
        {
            CalculatorContainer container = new CalculatorContainer();

            container.PushItem(5);
            Assert.That(container.Count() == 1);
            var lastItem = container.PopItem();

            Assert.AreEqual(5, lastItem);
        }