public void TestSumDouble()
        {
            double x = CodingQuiz_MathFunctions.Sum(10.5, 10.5);

            Assert.AreEqual(x, 21);
        }
        public void TestSumDecimal()
        {
            decimal x = CodingQuiz_MathFunctions.Sum(10.5M, 10.5M);

            Assert.AreEqual(x, 21);
        }
        public void TestSumInt()
        {
            int x = CodingQuiz_MathFunctions.Sum(2, 2);

            Assert.AreEqual(x, 4);
        }