TDD Workflow

Write tests first, code second.

1. The TDD Cycle

🔴 RED → Write failing test
    ↓
🟢 GREEN → Write minimal code to pass
    ↓
🔵 REFACTOR → Improve code quality
    ↓
   Repeat...

2. The Three Laws of TDD

Write production code only to make a failing test pass
Write only enough test to demonstrate failure
Write only enough code to make the test pass

3. RED Phase Principles

What to Write

| Focus | Example | |-------|---------| | Behavior | "should add two numbers" | | Edge cases | "should handle empty input" | | Error states | "should throw for invalid data" |

RED Phase Rules

Test must fail first
Test name describes expected behavior
One assertion per test (ideally)

4. GREEN Phase Principles

Minimum Code

| Principle | Meaning | |-----------|---------| | YAGNI | You Aren't Gonna Need It | | Simplest thing | Write the minimum to pass | | No optimization | Just make it work |

GREEN Phase Rules

Don't write unneeded code
Don't optimize yet
Pass the test, nothing more

5. REFACTOR Phase Principles

What to Improve

| Area | Action | |------|--------| | Duplication | Extract common code | | Naming | Make intent clear | | Structure | Improve organization | | Complexity | Simplify logic |

REFACTOR Rules

All tests must stay green
Small incremental changes
Commit after each refactor

6. AAA Pattern

Every test follows:

| Step | Purpose | |------|---------| | Arrange | Set up test data | | Act | Execute code under test | | Assert | Verify expected outcome |

7. When to Use TDD

| Scenario | TDD Value | |----------|-----------| | New feature | High | | Bug fix | High (write test first) | | Complex logic | High | | Exploratory | Low (spike, then TDD) | | UI layout | Low |

8. Test Prioritization

| Priority | Test Type | |----------|-----------| | 1 | Happy path | | 2 | Error cases | | 3 | Edge cases | | 4 | Performance |

9. Anti-Patterns

| ❌ Don't | ✅ Do | |----------|-------| | Skip the RED phase | Watch test fail first | | Write tests after | Write tests before | | Over-engineer initial | Keep it simple | | Multiple asserts | One behavior per test | | Test implementation | Test behavior |

10. AI-Augmented TDD

Multi-Agent Pattern

| Agent | Role | |-------|------| | Agent A | Write failing tests (RED) | | Agent B | Implement to pass (GREEN) | | Agent C | Optimize (REFACTOR) |

Remember: The test is the specification. If you can't write a test, you don't understand the requirement.

When to Use

This skill is applicable to execute the workflow or actions described in the overview.

Limitations

Use this skill only when the task clearly matches the scope described above.
Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.