String Calculator TDD Kata

This repository contains an implementation of the String Calculator TDD Kata, written in Dart following Test-Driven Development (TDD) principles.

The objective of this exercise is to demonstrate software craftsmanship by focusing on:

• Clean and readable code
• Small, well-defined functions
• Comprehensive unit tests
• Incremental development driven by tests

Topics

dart flutter tdd test-driven-development kata string-calculator unit-testing clean-code incubyte

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Problem Statement

Create a calculator with a method:

int add(String numbers)

The method takes a string containing numbers separated by delimiters and returns their sum, while following a specific set of rules described below. The implementation follows the Red-Green-Refactor TDD cycle, where each feature is developed incrementally:

Phase	Description
RED	Write a failing test first
GREEN	Write minimal code to make the test pass
REFACTOR	Clean up the code while keeping tests green

Why TDD?

• Confidence: Every line of code is covered by tests
• Design: Tests drive better API design
• Documentation: Tests serve as living documentation
• Maintainability: Refactoring is safe with comprehensive test coverage

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Features Implemented

#	Feature	Description	Example
1	Empty String	Returns 0 for empty input	add("") → 0
2	Single Number	Returns the number itself	add("1") → 1
3	Two Numbers	Sum of comma-separated numbers	add("1,2") → 3
4	Multiple Numbers	Handles any amount of numbers	add("1,2,3,4,5") → 15
5	Newline Delimiter	Supports \n as delimiter	add("1\n2,3") → 6
6	Custom Delimiter	Supports //[delimiter]\n syntax	add("//;\n1;2") → 3
7	Multi-char Delimiter	Supports //[***]\n syntax	add("//[***]\n1***2") → 3
8	Multiple Delimiters	Supports //[*][&]\n syntax	add("//[*][%]\n1*2&3") → 6
9	Input Validation	Handles empty parts gracefully	add("1,,3") → 4
10	Negative Numbers	Throws exception listing all negatives	add("-1,2,-3") → Exception

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Screenshots

Test Execution

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Usage Examples

import 'package:string_calculator/string_calculator.dart';

void main(List<String> arguments) {
  final calculator = StringCalculator();

  // Basic usage
  print(calculator.add(''));           // 0
  print(calculator.add('1'));          // 1
  print(calculator.add('1,2'));        // 3
  print(calculator.add('1,2,3,4,5'));  // 15

  // Newline delimiter
  print(calculator.add('1\n2,3'));     // 6

  // Custom delimiter
  print(calculator.add('//;\n1;2'));   // 3

  // Multi-character delimiter
  print(calculator.add('//[***]\n1***2***3'));  // 6

  // Multiple delimiters
  print(calculator.add('//[*][&]\n1*2&3'));     // 6

  // Input validation - empty parts ignored
  print(calculator.add('1,,3'));       // 4

  // Negative numbers throw exception
  try {
    calculator.add('-1,2,-3');
  } catch (e) {
    print(e);  // Exception: negative numbers not allowed -1,-3
  }
}

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Running Tests

# Run all tests
dart test

# Run tests with verbose output
dart test --reporter expanded

# Run with coverage
dart test --coverage

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Test Results

00:00 +0: loading /Users/avishal/Desktop/personal/tdd_string_calculator/test/tdd_string_calculator_test.dart
00:00 +0: returns 0 for empty string
00:00 +1: returns number itself for single number
00:00 +2: returns sum of two comma separated numbers
00:00 +3: handles any amount of numbers
00:00 +4: handles new lines between numbers
00:00 +5: supports custom delimiter
00:00 +6: supports multi-character delimiter
00:00 +7: supports multiple delimiters
00:00 +8: supports multiple multi-character delimiters
00:00 +9: throws exception for single negative number
00:00 +10: throws exception listing all negative numbers
00:00 +11: throws exception for invalid input
00:00 +12: ignores empty parts between delimiters
00:00 +13: All tests passed!

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Requirements

• Dart SDK: ^3.9.0

Getting Started

# Clone the repository
git clone https://github.com/Aniket76/string_calculator.git

# Navigate to project
cd string_calculator

# Get dependencies
dart pub get

# Run tests
dart test --reporter expanded

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TDD Commit History

Each feature follows the RED-GREEN-REFACTOR pattern. View the complete commit history:

git log --oneline

Sample Commits:

f85b6b4 RED: test two comma-separated numbers sum
b38344c GREEN: split by comma and sum numbers
714a6e2 REFACTOR: created functions for better handling

3cf7841 RED: handles any amount of numbers
1a44564 GREEN: already works with existing implementation
...

Total: 31 commits demonstrating incremental TDD development.

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Author

Aniket Vishal

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License

This project is open source and available under the MIT License.