public void Test_Positive()
        {
            var controller = new ZController();

            var t = controller.Get(30);

            Assert.AreEqual(15, t.ElementAt(0));
            Assert.AreEqual(30, t.ElementAt(1));
        }
        public void Test_Negative()
        {
            var controller = new ZController();

            var t = controller.Get(-2);

            Assert.AreEqual(1, t.Count());

            Assert.AreEqual(15, t.ElementAt(0));
        }