String Calculator TDD Kata

Overview

This is my solution to the Incubyte String Calculator TDD Kata.
The goal of the kata is to implement a string calculator with the following capabilities:

• Return 0 for an empty string.
• Return the sum of numbers provided as a string.
• Support one or more numbers separated by commas or newlines.
• Support custom delimiters specified in the format: //[delimiter]\n[numbers].
• Throw an exception for negative numbers, listing all negatives.

This implementation was built following the TDD approach, with incremental tests and refactoring.

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Features Implemented

1. Empty String

   calculator.add("") # => 0

2. Single Number

   calculator.add("5") # => 5

3. Multiple Numbers

   calculator.add("1,2,3") # => 6

4. Newline as Delimiter

   calculator.add("1\n2,3") # => 6

5. Custom Delimiter

   calculator.add("//;\n1;2") # => 3

6. Negative Number Handling

   calculator.add("-1,2") 
   # Raises: "negative numbers not allowed -1"
   
   calculator.add("2,-4,3,-5") 
   # Raises: "negative numbers not allowed -4,-5"

How to Run

1. Install dependencies (RSpec): gem install rspec

2. Run tests: rspec spec/string_calculator_spec.rb --format documentation