String Calculator

String Calculator

The following is a TDD Kata - an exercise in coding, refactoring and test-first - that you should apply daily for at least 15 minutes (I do 30).
Before you start:

Try not to read ahead.
Do one task at a time. 
    The trick is to learn to work incrementally.
Make sure you only test for correct inputs. 
    There is no need to test for invalid inputs for this kata

String Calculator

• 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 ';'.
  • the 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 stop here if you are a beginner.
  • Continue if you can finish the steps so far in less than 30 minutes.
• Numbers bigger than 1000 should be ignored, so adding 2 + 1001 = 2
• Delimiters can be of any length with the following format: "//[delimiter]\n" for example: "//[***]\n1***2***3" should return 6
• Allow multiple delimiters like this: "//[delim1][delim2]\n" for example "//[*][%]\n1*2%3" should return 6.
  • make sure you can also handle multiple delimiters with length longer than one char