Test-Driven Development

Write the test first. Make it pass. Clean up. Run the tests. Every time.

The Cycle

Every code change follows red-green-refactor:

1. Red — Write a test for the next behavior. Run it. Watch it fail.
2. Green — Write the minimum code to make the test pass. Nothing more.
3. Refactor — Clean up duplication and improve clarity. Tests stay green.
4. Repeat — Pick the next behavior. Start another cycle.

Run tests after every step. Not just at the end — after every step.

1. Start With a Failing Test