This classic kata guides you step by step through the implementation of a calculator that receives a String as input. It is a good exercise on refactoring and incremental implementation. It is also a good candidate for practising TDD.
Create a function add that takes a String and returns a String:
String add(String number)
- The method can take 0, 1 or 2 numbers separated by comma, and returns their sum.
- An empty string will return “0”.
- Example of inputs: "", "1", "1.1,2.2".
Allow the add method to handle an unknow number of arguments.
Allow the add method to handle newlines as separators:
- "1\n2,3" should return "6".
- "175.2,\n35" is invalid and should return the message "Number expected but '\n' found at position 6."
Don’t allow the input to end in a separator.
- "1,3," is invalid and should return the message Number expected but EOF found.
Allow the add method to handle a different delimiter. To change the delimiter, the beginning of the input will contain a separate line that looks like this:
//[delimiter]\n[numbers]
- "//;\n1;2" should return "3"
- "//|\n1|2|3" should return "6"
- "//sep\n2sep3" should return "5"
- "//|\n1|2,3" is invalid and should return the message "'|' expected but ',' found at position 3."
All existing scenarios should work as before.
Calling add with negative numbers will return the message "Negative not allowed : " listing all negative numbers that were in the list of numbers.
- "-1,2" is invalid and should return the message "Negative not allowed : -1"
- "2,-4,-5" is invalid and should return the message "Negative not allowed : -4, -5"
Calling add with multiple errors will return all error messages separated by newlines.
- "-1,,2" is invalid and return the message "Negative not allowed : -1\nNumber expected but ',' found at position 3."
- "-1,,-2" is invalid and return the message "Negative not allowed : -1\nNumber expected but ',' found at position 3.\nNegative not allowed : -2"