🧪 String Calculator TDD Kata

This is a simple Test-Driven Development (TDD) exercise to implement a string-based calculator that parses numbers and returns their sum.

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📌 Tips

• ✅ Start with the simplest test case of an empty string.
• ✅ Move to one and two numbers as next steps.
• ✅ Solve problems in the simplest manner so that you're forced to write tests you may not have initially thought of.
• ✅ Refactor your code after each passing test.

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🧩 Problem Statement

Create a simple String Calculator with the following method signature:

int add(string numbers)

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📥 Input

• A string containing numbers separated by delimiters such as:
  • Commas ,
  • New lines \n
  • Custom delimiters (defined by the user)

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📤 Output

• An integer which is the sum of the numbers in the input string.

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✅ Examples

Input	Output
""	0
"1"	1
"1,5"	6
"1\n2,3"	6
"//;\n1;2"	3

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🧠 Features to Implement

1. ✅ Return 0 for an empty string.
2. ✅ Return the number itself if only one number is provided.
3. ✅ Sum of two or more comma-separated numbers.
4. ✅ Allow any number of comma-separated numbers.
5. ✅ Allow new lines between numbers (e.g. "1\n2,3").
6. ✅ Support custom delimiters:
   • Format: "//[delimiter]\n[numbers]"
   • Example: "//;\n1;2" should return 3.
7. ❌ If any negative numbers are passed, the method should throw an exception:
   • Error message: "negative numbers not allowed: <negative_number>"
   • If multiple negatives are found, list all in the message:
     • Example: "negative numbers not allowed: -1, -5"

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🔁 Suggested TDD Workflow

1. Write a failing test.
2. Write just enough code to make it pass.
3. Refactor for cleanliness.
4. Commit after each step to track progress clearly.

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Solution

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🛠 Tech Stack

• Language: JavaScript (Node.js)
• Test Framework: Node’s built-in assert module (basic, beginner-friendly)
• Git: For version control and committing each step

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🚀 How to Run

1. Clone the repo:

   git clone https://github.com/Satish980/string-calculator-tdd-kata
   cd string-calculator

2. Run the code using Node:

   node src/calculator.js

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🧪 How to Test

I’ve used Node’s built-in assert module.

1. To run tests:

   node tests/calculator.test.js

2. Example test:

   const assert = require('assert');
   assert.strictEqual(add("1,2,3"), 6);

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🖥 Sample Run

Below is a screenshot of the calculator running and passing all test cases:

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📁 Project Structure

string-calculator-tdd-kata/
├── src/calculator.js       # main calculator logic
├── tests/calculator.test.js        # test cases
└── README.md      # project documentation

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