---

name: test-driven-development description: Guide for RED-GREEN-REFACTOR cycle. Use when writing tests or implementing features with TDD. license: MIT

Test-Driven Development

Follow the RED-GREEN-REFACTOR cycle for all development work.

Process

1. RED - Write a Failing Test

• Write a test that describes the desired behavior
• Run the test to confirm it fails
• The test should fail for the right reason

2. GREEN - Make It Pass

• Write the minimum code to make the test pass
• Don't over-engineer or add extra features
• Focus only on passing the current test

3. REFACTOR - Clean Up

• Improve code quality without changing behavior
• Remove duplication
• Improve naming and structure
• All tests should still pass

Anti-Patterns to Avoid

• Writing code before tests
• Writing multiple tests before making any pass
• Refactoring while tests are failing
• Testing implementation details instead of behavior
• Skipping the refactor step

Best Practices

• Keep tests fast and isolated
• Test behavior, not implementation
• One assertion per test when possible
• Use descriptive test names
• Mock external dependencies