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

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

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

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

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

            try
            {
                // act
                var result = calculator.Add(input);
            }
            catch (ArgumentException ex)
            {
                //assert
                Assert.AreEqual(expected, ex.Message);
            }
        }
        private static void Main(string[] args)
        {
            ICalculator theObject = new Business.Calculator();

            while (true)
            {
                Console.WriteLine("Enter equation for processing:");

                var userInput = Console.ReadLine();
                try
                {
                    switch (userInput)
                    {
                    case "help":
                    {
                        Console.WriteLine("We only do basic addition, " +
                                          "multiplication, and division \n " +
                                          "e.g. 5 + 2 \n Only 2 numbers and " +
                                          "must be separated by a space.");
                        break;
                    }

                    case "file":
                    {
                        Console.WriteLine("File path:");
                        var filePath       = Console.ReadLine();
                        var equationResult = theObject.Proccess(filePath, true, null);
                        Console.WriteLine(equationResult);
                        break;
                    }

                    default:
                        var result = theObject.Proccess(userInput, false, new object());
                        Console.WriteLine(result);
                        break;
                    }
                }
                catch (Exception)
                {// Should never happen
                }
            }
        }