Test-Driven Development (TDD)

Overview

Write the test first. Watch it fail. Write minimal code to pass.

Core principle: If you didn't watch the test fail, you don't know if it tests the right thing.

Violating the letter of the rules is violating the spirit of the rules.

Quick Start

1. Write one failing test describing desired behavior
2. Run it - confirm it fails for the right reason
3. Write minimal code to pass
4. Run it - confirm it passes
5. Refactor if needed, keeping tests green

When to Use