public void TestPush()
        {
            var sut = new SungStack <int>();

            sut.Push(1);
            sut.Push(2);
            sut.Push(3);

            int[] expected = { 3, 2, 1 };
            Assert.True(expected.SequenceEqual(sut.Traverse().ToArray()));
        }
        public void TestPop()
        {
            var sut = new SungStack <int>();

            sut.Push(1);
            sut.Push(2);
            sut.Push(3);

            var popped = sut.Pop();

            Assert.Equal(3, popped);
            Assert.True(new[] { 2, 1 }.SequenceEqual(sut.Traverse().ToArray()));

            popped = sut.Pop();
            Assert.Equal(2, popped);
            Assert.True(new[] { 1 }.SequenceEqual(sut.Traverse().ToArray()));

            popped = sut.Pop();
            Assert.Equal(1, popped);
            Assert.True(new int[] {}.SequenceEqual(sut.Traverse().ToArray()));

            Assert.Throws <InvalidOperationException>(() => sut.Pop());
        }