test-driven-development

name: test-driven-development description: Test-driven development. Follow the RED-GREEN-REFACTOR cycle - write failing tests first, then write minimal code to pass, then refactor. Use when writing new features or fixing bugs.

Test-Driven Development Skill

Strictly follow the TDD RED-GREEN-REFACTOR cycle.

Core Principles

1. Always Write Tests First - No production code without a failing test
2. Minimal Implementation - Only write code to make the test pass
3. Continuous Refactoring - Refactor immediately after tests pass

Workflow

RED Phase (Failing Test)

1. Define the behavior to implement
2. Write a test describing that behavior
3. Run the test, confirm it fails
4. Confirm failure is due to missing functionality, not test errors

GREEN Phase (Passing Test)

1. Write the simplest code to make the test pass
2. Don't over-engineer
3. Run the test, confirm it passes
4. Commit immediately

REFACTOR Phase

1. Check for code duplication
2. Check naming clarity
3. Check single responsibility
4. Run tests to confirm nothing broke
5. Commit refactoring

Anti-Pattern Warnings

Avoid these behaviors:

• ❌ Writing code before tests
• ❌ Writing too many tests at once
• ❌ Refactoring before tests pass
• ❌ Skipping the failing test verification step

Test Naming Convention

test_[feature]_[scenario]_[expected_result]

Examples:

• test_login_with_valid_credentials_returns_token
• test_login_with_invalid_password_returns_401