String Calculator – TDD Kata (Dart)

This repository contains a robust implementation of the String Calculator Kata using Test-Driven Development (TDD) in Dart. The project follows an incremental approach to string parsing, validation, and mathematical logic.

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📌 Project Overview

The StringCalculator class provides a flexible add method capable of processing strings with various delimiters, handling edge cases, and enforcing specific mathematical constraints.

The codebase is:

• Fully unit-tested
• Explicitly documented using DartDoc (///) comments
• Designed for readability, maintainability, and robustness

This implementation strictly follows the Red → Green → Refactor cycle, ensuring every feature is backed by a test and clearly documented.

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🧪 What is TDD and TDD Process?

Test-Driven Development (TDD):

This project was developed using strict TDD discipline:

• Each feature starts with a failing test (RED)
• Minimal implementation added to pass the test (GREEN)
• Code improved without changing behavior (REFACTOR)

This process ensures:

• High test coverage
• Clean, maintainable code
• Confidence in refactoring
• Clear traceability between requirements, tests, and implementation

The commit history demonstrates the full RED–GREEN–REFACTOR progression.

🚀 Supported Features

Based on the implemented test suite, the calculator supports the following:

Feature	Input Example	Result
Empty String	""	0
Single Number	"5"	5
Sum of Two Numbers	"1,2"	3
Multiple Numbers	"1,2,3,4"	10
Newline Delimiters	"1\n2,3"	6
Custom Delimiters	"//;\n1;2"	3
Negative Numbers	"1,-2,3"	Throws Exception
Upper Bound Limit	"2,1001"	2 (Numbers > 1000 ignored)
Multi-character Delimiters	"//[***]\n1***2***3"	6
Multiple Delimiters	"//[*][%]\n1*2%3"	6
Empty Tokens Between Delimiters	"1,,3"	4
Invalid Input	"1,a,3"	Throws Exception

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🧾 Code Documentation

All public classes and methods are documented using DartDoc (///) syntax.

The documentation clearly describes:

• Class responsibilities
• Method behavior
• Supported input formats
• Parameters and return values
• Thrown exceptions
• Usage examples

Example (from source code):

/// A calculator that adds numbers from a string input.
///
/// Supports multiple delimiters and custom delimiter syntax.
/// Numbers greater than 1000 are ignored.
/// Throws an exception if negative numbers are found.
class StringCalculator {
  /// Adds numbers in the given string and returns the sum.
  ///
  /// Parameters:
  /// - [numbers]: A string containing numbers separated by delimiters
  ///
  /// Returns:
  /// - The sum of all valid numbers (≤ 1000)
  ///
  /// Throws:
  /// - [Exception] if negative or invalid numbers are present
  int add(String numbers) { ... }
}

🛠️ Installation & Usage

1. Prerequisites

Ensure you have the Dart SDK installed on your machine.

2. Run Tests

To verify the implementation against the test suite, run:

dart test
or
fvm dart test

🧪 Usage Example

import 'package:string_calculator_tdd/string_calculator.dart';

void main() {
  final calc = StringCalculator();

  print(calc.add(""));              // 0
  print(calc.add("1,2,3"));         // 6
  print(calc.add("//;\n1;2"));      // 3
  print(calc.add("2,1005"));        // 2 (1005 is ignored)
}

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screenshots/ ├── tests_passing.png ├── commit_history.png └── test_coverage.png (optional)

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🖥 🧪 🧪

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Author

Parth Pitroda
GitHub: https://github.com/hiopitroda Date: 24 January 2026 Assessment: Incubyte TDD Kata

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