String Calculator (Ruby TDD)

A Ruby implementation of String Calculator using Test‑Driven Development (TDD).

🧪 Features

• add("") returns 0
• add("1") returns 1
• add("1,2") returns 3
• Supports an arbitrary number of numbers
• Supports newlines as delimiters, e.g. "1\n2,3"
• Allows custom single-character delimiter syntax: "//;\n1;2"
• Throws an exception for negative numbers with a message listing all negatives
• Ignores numbers greater than 1000
• Supports multi-character delimiters: "//[***]\n1***2***3"

Getting Started

Prerequisites

• Ruby (≥ 2.5)
• Bundler (optional but recommended)

Installation

git clone https://github.com/jaykava/string_calculator_ruby_tdd.git
cd string_calculator_ruby_tdd
bundle install   # if using Bundler

Running Tests

rspec

Usage

• You can manually use the calculator with:

require_relative 'string_calculator'

calc = StringCalculator.new
puts calc.add("1,2,3")  # => 6

Project Structure

string_calculator_ruby_tdd/
└── lib/
    └── string_calculator.rb   # implementation
└── spec/
    └── string_calculator_spec.rb  # RSpec tests

Examples

calc = StringCalculator.new
calc.add("")                           # => 0
calc.add("4")                          # => 4
calc.add("1,2,3,4")                    # => 10
calc.add("1\n2,3")                     # => 6
calc.add("//;\n2;5")                   # => 7
calc.add("2,1001")                     # => 2
calc.add("//[***]\n1***2***3")         # => 6

• Negative numbers:

calc.add("1,-2,3,-4")
# => raises RuntimeError: "negatives not allowed: -2, -4"