public void TestMethodADD()
        {
            var math = new MathDemo.Math();

            Assert.AreEqual(10, math.Add(8, 2));
            Assert.AreEqual(100, math.Add(20, 80));
        }
        public void TestMethodSubtract()
        {
            var math = new MathDemo.Math();

            Assert.AreEqual(6, math.Subtract(8, 2));
            Assert.AreEqual(-60, math.Subtract(20, 80));
        }