String Calculator Kata
The following is a TDD Kata, an exercise in coding, refactoring and test-first.
The goal is to solve the exercise in your own best way, showing us how you approch problems and your workflow. We may give more value to how you reached the solution with respect to the solution itself.
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.
- Commit your code on GitHub or any other SCM repository you prefer.
- Release your work under an OSI-approved open-source license of your choice.
- Disable Copylot and don't watch others solutions while trying to solve this kata, you'll make it harder for us to asses your skills.
The kata
Step 1: the simplest thing
Create a simple String calculator with a method int add(String numbers).
- The string argument can contain 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.
Step 2: handle an unknown amount of numbers
Allow the add() method to handle an unknown amount of numbers.
Step 3: handle new lines between 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)
Step 4: support different delimiters
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.
Step 5: negative numbers
Calling add() with a negative number will throw an exception "negatives not allowed" - and the negative that was passed.
For example add("1,4,-1") should throw an exception with the message "negatives not allowed: -1".
If there are multiple negatives, show all of them in the exception message.
Step 6: ignore big numbers
Numbers bigger than 1000 should be ignored, so adding 2 + 1001 = 2
Step 7: delimiters length
Delimiters can be of any length with the following format: //[delimiter]\n for example: //[***]\n1***2***3 should return 6
General requirements
We would love to see your submission written in JavaScript. Although, you can use whatever language and framework you want. Use something that you know well.
IMPORTANT: Provide a README with instructions on how to compile and run the application.
CODE SUBMISSION: Add the code to your own Github account and send us the link.
Credits to Roy Osherove for the original idea.