Test-Driven Development (TDD)

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

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

When to Use

• New features, bug fixes, refactoring, behavior changes

Exceptions (confirm with user): throwaway prototypes, generated code, configuration files.

Red-Green-Refactor Cycle

RED — Write Failing Test

Write one minimal test for one behavior.