String Calculator Kata (via Roy Osherove)

• Create a simple String calculator with a method int Add(string numbers). The method can take 0, 1 or 2 numbers, and will return their sum (for an empty string it will return 0). For example "" or "1" or "1,2"
  • Start with the simplest test case of an empty string and move to 1 and two numbers
  • Remember to solve things as simply as possible so that you force yourself to write tests you did not think about
  • Remember to refactor after each passing test
• Allow the Add method to handle an unknown amount of numbers
• Allow the Add method to handle new lines between numbers (instead of commas).
  • the following input is ok: "1\n2,3" (will equal 6)
  • the following input is NOT ok: "1,\n" (not need to prove it - just clarifying)
• Support different delimiters. To change a delimiter, the beginning of the string will contain a separate line that looks like this: //[delimiter]\n[numbers...], for example //;\n1;2 should return three where the default delimiter is ; .
  • he first line is optional. all existing scenarios should still be supported
• Calling Add with a negative number will throw an exception "negatives not allowed" - and the negative that was passed.
  • if there are multiple negatives, show all of them in the exception message