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name: tdd-workflow description: Test-Driven Development guidance. Use when writing code, implementing features, or fixing bugs in projects that follow TDD methodology. Provides the Red-Green-Refactor cycle structure.

TDD Workflow Skill

Guidance for Test-Driven Development methodology.

The Core Cycle

RED → GREEN → REFACTOR (repeat)

Phase 1: RED - Write Failing Test

Purpose: Define behavior before implementation.

Actions:

1. Create/open test file
2. Write test for ONE behavior
3. Run test
4. Verify FAILURE (if it passes, test is wrong)

Common mistakes: Tests pass immediately, testing implementation not behavior, writing too many tests at once

Phase 2: GREEN - Make It Pass

Purpose: Write MINIMUM code to pass test.

Actions:

1. Implement just enough to pass
2. No extra features, no optimization
3. Run tests, verify PASS

Common mistakes: Over-engineering, adding untested features, "while I'm here" additions

Phase 3: REFACTOR - Improve Quality

Purpose: Clean up while keeping tests green.

Actions:

1. Identify improvements: duplication, naming, complex logic, long functions
2. Make ONE change
3. Run tests
4. If green, continue. If red, undo.

Checklist: Extract methods, rename variables, remove duplication (DRY), simplify conditionals, add type safety

Test Patterns

Arrange-Act-Assert (AAA):

1. Arrange: Set up test data
2. Act: Execute the behavior
3. Assert: Verify result

Given-When-Then (BDD): Structure nested describes for readability

Coverage Commands

Anti-Patterns to Avoid

1. Test After: Writing code first defeats TDD purpose
2. Testing Implementation: Test WHAT it does, not HOW (test behavior, not internal calls)
3. Brittle Tests: Use resilient assertions (e.g., toContainEqual not array index checks)
4. No Refactoring: Skipping refactor creates technical debt

Quick Reference

• RED: "What should it do?" → Write failing test
• GREEN: "Does it work?" → Write minimal code
• REFACTOR: "Is it clean?" → Improve structure

For detailed code examples, see examples.md in this skill directory.

Integration

Works with:

• context-awareness: Project-specific coverage targets
• code-styleguides: Language-specific test patterns