String Calculator TDD Kata

Tips:

• Start with the simplest test case of an empty string and move to one and two numbers.
• Remember to solve problems in a simple manner so that you force yourself to write tests you did not think about.
• Remember to refactor after each passing test.

Steps:

1. Create a simple String calculator with a method signature like this:

   int add(String numbers)

   • Input: a string of comma-separated numbers.
   • Output: an integer, sum of the numbers.

2. Examples:

   • Input: "", Output: 0
   • Input: "1", Output: 1
   • Input: "1,5", Output: 6
   • Allow the add method to handle any amount of numbers.

3. Allow the add method to handle new lines between numbers (instead of commas).

   • Example: "1\n2,3" should return 6.

4. Support different delimiters:

   • To change the delimiter, the beginning of the string will contain a separate line that looks like this: "//[delimiter]\n[numbers…]".
   • Example: "//;\n1;2" where the delimiter is ";" should return 3.

5. Negative number handling:

   • Calling add with a negative number will throw an exception: "negative numbers not allowed <negative_number>".
   • If there are multiple negative numbers, show all of them in the exception message, separated by commas.

6. Ignore numbers greater than 1000:

   • Numbers greater than 1000 should be ignored in the sum calculation.
   • Example: "2,1001" should return 2.

7. Using * as delimiter return Multiplication :

   • When you use * as delimiter it should return multiplication.
   • Example: "//*\n3*2*5" should return 30.

8. Delimiters of any length:

   • Delimiters can be of any length if enclosed in square brackets.
   • Example: "//[***]\n1***2***3" where the delimiter is "***" should return 6.

9. Track how many times add() is invoked:

   • Implement a method getCalledCount() that returns the number of times add() method was called.

10. Support multiple delimiters:

• Allow multiple delimiters to be specified using square brackets.
• Example: "//[*][%]\n1*2%3" should return 6.

11. Handle multiple delimiters with length longer than one character:

• Delimiters can also be longer than one character.
• Example: "//[**][%%]\n1**2%%3" should return 6.

Remember to follow the Test-Driven Development (TDD) cycle:

• Write a failing test.
• Write the simplest code to make it pass.
• Refactor the code while keeping all tests passing.