What I Do
- Guide you through the RED-GREEN-REFACTOR cycle
- Write failing tests first, then implementation
- Ensure tests are meaningful and not just passing
- Prevent common TDD anti-patterns
When to Use Me
Use this skill when:
- Implementing new features
- Fixing bugs (write a failing test that reproduces the bug first)
- Refactoring existing code (ensure tests exist first)
The TDD Cycle
1. RED - Write a Failing Test
1. Write a test for the NEXT small piece of functionality
2. Run the test - it MUST fail
3. If it passes, either:
- The functionality already exists, or
- The test is wrong
The test should:
- Test ONE thing
- Have a descriptive name explaining the behavior
- Follow Arrange-Act-Assert pattern
2. GREEN - Make It Pass
1. Write the MINIMUM code to make the test pass
2. Don't worry about elegance yet
3. Hardcoding is acceptable temporarily
4. Run the test - it MUST pass
Rules:
- Only write code that makes a failing test pass
- Don't add functionality without a test
- Keep changes small
3. REFACTOR - Clean Up
1. Improve code quality while keeping tests green
2. Remove duplication
3. Improve naming
4. Extract methods/functions
5. Run tests after EVERY change
Anti-Patterns to Avoid
| Anti-Pattern | Problem | Solution | |--------------|---------|----------| | Writing tests after code | Tests validate implementation, not behavior | Always write test first | | Testing implementation details | Brittle tests that break on refactor | Test public behavior only | | Large test steps | Hard to identify what broke | Smaller increments | | Skipping refactor phase | Technical debt accumulates | Always refactor after green | | Testing trivial code | Wasted effort | Focus on logic and edge cases |
Test Structure
describe('ComponentName', () => {
describe('methodName', () => {
it('should [expected behavior] when [condition]', () => {
// Arrange - set up test data
// Act - call the method
// Assert - verify the result
});
});
});
Commit Rhythm
1. RED: Don't commit (test is failing)
2. GREEN: Commit with "test: add test for X"
3. REFACTOR: Commit with "refactor: improve X"