Test-Driven Development (TDD)

Overview

Write the test first. Watch it fail. Then write the code.

TDD is not about testing - it's about design. Writing tests first forces you to think about the interface before the implementation.

When to Use

• Implementing any new function, method, or feature
• Asked to "write code now, add tests later"
• Fixing a bug (write test that reproduces it first)
• Refactoring existing code

The Iron Rule