public void TestIsInteger1()
        {
            bool isInteger = ReverseNumberDigits.IsInteger("2793562347856293476");

            bool expectedAnswer = true;

            Assert.AreEqual(expectedAnswer, isInteger);
        }
        public void TestIsInteger3()
        {
            bool isInteger = ReverseNumberDigits.IsInteger("+27785629");

            bool expectedAnswer = true;

            Assert.AreEqual(expectedAnswer, isInteger);
        }
        public void TestIsInteger4()
        {
            bool isInteger = ReverseNumberDigits.IsInteger("+277abc629");

            bool expectedAnswer = false;

            Assert.AreEqual(expectedAnswer, isInteger);
        }
        public void TestIsInteger2()
        {
            bool isInteger = ReverseNumberDigits.IsInteger("-27935623478562234234234545345365469199889");

            bool expectedAnswer = true;

            Assert.AreEqual(expectedAnswer, isInteger);
        }