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 signature:

int add(String numbers)

The method can take up to two numbers, separated by commas, and will return their sum. For an empty string it will return 0.

For example "" or "1" or "1,2" as inputs.

Hints:

• Start with the simplest test case of an empty string and move to one 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)

"1\n2,3" will equal 6.

Disallow negative numbers

Calling add with a negative number will throw an exception.

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 3 where the default delimiter is ;.

The first line is optional. All existing scenarios should still be supported