public void WhenStringHasMultipleNumbersSeperatedByCommaReturnTheSum(string input, int expected)
        {
            // arrange
            var calculator = new StringCalculator.Business.Calculator();

            // act
            var result = calculator.Add(input);

            //assert
            Assert.AreEqual(expected, result);
        }
        public void WhenStringIsEmptyReturnZero(string input, int expected)
        {
            // arrange
            var calculator = new StringCalculator.Business.Calculator();

            // act
            var result = calculator.Add(input);

            //assert
            Assert.AreEqual(expected, result);
        }
        public void WhenStringHasOneNumberReturnTheNumber()
        {
            var input = "5";

            // arrange
            var calculator = new StringCalculator.Business.Calculator();

            // act
            var result = calculator.Add(input);

            //assert
            Assert.AreEqual(int.Parse(input), result);
        }