testing-patterns
Write effective tests with proper structure and coverage. Use when writing unit tests, integration tests, or improving test quality.
When & Why to Use This Skill
The Testing Patterns skill empowers developers to build robust, maintainable software by implementing industry-standard testing methodologies. It provides structured guidance on the AAA (Arrange-Act-Assert) pattern, consistent naming conventions, and strategic mocking, ensuring high-quality code coverage across unit and integration tests while eliminating flaky or redundant test cases.
Use Cases
- Standardizing Test Structure: Utilizing the AAA (Arrange-Act-Assert) pattern to create readable and organized unit tests for complex business logic.
- Improving Test Maintainability: Applying descriptive naming conventions (e.g., test_unit_scenario_result) to ensure test suites serve as clear documentation for future developers.
- Optimizing Integration Testing: Designing effective tests for API endpoints, database operations, and external service interactions to verify system-wide reliability.
- Strategic Mocking: Implementing fast and deterministic tests by correctly mocking external APIs, databases, and time-dependent functions while avoiding brittle implementation-detail testing.
- Quality Audit and Coverage: Evaluating existing test suites against a quality checklist to identify gaps in critical business logic and reduce technical debt from low-value tests.
| name | testing-patterns |
|---|---|
| description | Write effective tests with proper structure and coverage. Use when writing unit tests, integration tests, or improving test quality. |
| allowed-tools | Read, Write, Edit, Grep, Glob, Bash |
Testing Patterns Skill
Help write clear, maintainable, effective tests.
Test Structure (AAA Pattern)
// Arrange - Set up test data and conditions
// Act - Execute the code under test
// Assert - Verify the expected outcome
Naming Convention
test_[unit]_[scenario]_[expected result]
Examples:
- test_calculateTotal_withEmptyCart_returnsZero
- test_login_withInvalidPassword_throwsAuthError
- test_fetchUser_whenNotFound_returns404
What to Test
Unit Tests
- Pure functions and calculations
- Business logic
- Edge cases and boundaries
- Error conditions
Integration Tests
- API endpoints
- Database operations
- External service interactions
- Authentication flows
Do NOT Test
- Framework/library internals
- Private methods directly
- Trivial getters/setters
- Third-party code
Test Quality Checklist
- Tests one thing only
- Clear test name describes behavior
- Independent (no test order dependency)
- Fast (mock external dependencies)
- Deterministic (no flaky tests)
- Readable (future you is the audience)
Mocking Guidelines
Mock:
- External APIs
- Database (for unit tests)
- Time/dates
- Random values
- File system (when appropriate)
Don't mock:
- The thing you're testing
- Simple value objects
- Everything (leads to brittle tests)
Coverage Strategy
Focus on:
- Critical business logic: 90%+
- Happy paths: 100%
- Error paths: 80%+
- Edge cases: Case by case
Avoid:
- Chasing 100% blindly
- Testing implementation details
- Duplicate coverage