Overview
The testing-patterns skill provides comprehensive guidance on building reliable test suites. It covers the testing pyramid, AAA pattern, test type selection, and best practices for unit, integration, and E2E testing.What This Skill Provides
- Testing Pyramid: Understanding the balance between unit, integration, and E2E tests
- AAA Pattern: Arrange-Act-Assert structure for clear tests
- Test Type Selection: When to use unit vs integration vs E2E
- Unit Test Principles: Fast, isolated, repeatable tests
- Integration Testing: API, database, and service integration
- Mocking Strategies: When and how to mock dependencies
- Test Organization: Naming conventions and file structure
- Test Data Management: Factories, fixtures, and builders
Key Concepts
Testing Pyramid
AAA Pattern
| Step | Purpose |
|---|---|
| Arrange | Set up test data |
| Act | Execute code under test |
| Assert | Verify expected outcome |
Test Type Selection
| Type | Best For | Speed |
|---|---|---|
| Unit | Pure functions, logic | Fast (under 50ms) |
| Integration | API, DB, services | Medium |
| E2E | Critical user flows | Slow |
Use Cases
When to Use This Skill
- Setting up a test suite for a new project
- Deciding what types of tests to write
- Improving test coverage and quality
- Debugging flaky tests
- Implementing mocking strategies
- Organizing test code structure
Example Scenarios
- New Feature: “Add tests for the user authentication feature”
- Refactoring: “Make these tests more maintainable”
- Coverage: “What should I test in this module?”
- Mocking: “Should I mock this database call?”
Best Practices
Unit Tests
| Principle | Meaning |
|---|---|
| Fast | < 100ms each |
| Isolated | No external deps |
| Repeatable | Same result always |
| Self-checking | No manual verification |
| Timely | Written with code |
What to Test
| Test | Don’t Test |
|---|---|
| Business logic | Framework code |
| Edge cases | Third-party libs |
| Error handling | Simple getters |
Mocking Principles
| Mock | Don’t Mock |
|---|---|
| External APIs | The code under test |
| Database (unit) | Simple dependencies |
| Time/random | Pure functions |
| Network | In-memory stores |
Anti-Patterns to Avoid
- ❌ Testing implementation details instead of behavior
- ❌ Duplicating test code without using factories
- ❌ Complex test setup (simplify or split)
- ❌ Ignoring flaky tests
- ❌ Skipping cleanup between tests
Related Skills
- tdd-workflow: Test-Driven Development cycle
- webapp-testing: E2E and Playwright testing
- code-review-checklist: Testing coverage in reviews
- clean-code: Clean test code principles
Which Agents Use This Skill
- test-engineer: Primary user for all testing activities
- qa-automation-engineer: Uses for automated test development
Test Organization
Naming Conventions
| Pattern | Example |
|---|---|
| Should behavior | ”should return error when…” |
| When condition | ”when user not found…” |
| Given-when-then | ”given X, when Y, then Z” |
File Structure
Tools Available
- Read, Write, Edit: For working with test files
- Glob, Grep: For searching test patterns
- Bash: For running test commands
Scripts
| Script | Purpose | Command |
|---|---|---|
scripts/test_runner.py | Run tests with validation | python scripts/test_runner.py . |
Remember: Tests are documentation. If someone can’t understand what the code does from the tests, rewrite them.