testing-guide

This skill provides testing pyramid standards and best practices for systematic testing.

Quick Reference

Testing Pyramid

                    ┌─────────┐
                    │   E2E   │  ← Fewer, slower (3%)
                   ─┴─────────┴─
                  ┌─────────────┐
                  │     ST      │  ← System (7%)
                 ─┴─────────────┴─
                ┌─────────────────┐
                │       IT        │  ← Integration (20%)
               ─┴─────────────────┴─
              ┌─────────────────────┐
              │         UT          │  ← Unit (70%)
              └─────────────────────┘

Test Levels Overview

| Level | Scope | Speed | Dependencies | |-------|-------|-------|-------------| | UT | Single function/class | < 100ms | Mocked | | IT | Component interaction | 1-10s | Real DB (containerized) | | ST | Full system | Minutes | Production-like | | E2E | User journeys | 30s+ | Everything real |

Coverage Targets

| Metric | Minimum | Recommended | |--------|---------|-------------| | Line | 70% | 85% | | Branch | 60% | 80% | | Function | 80% | 90% |

Detailed Guidelines

For complete standards, see:

• Testing Pyramid

Naming Conventions

File Naming

[ClassName]Tests.cs       # C#
[ClassName].test.ts       # TypeScript
[class_name]_test.py      # Python
[class_name]_test.go      # Go

Method Naming

[MethodName]_[Scenario]_[ExpectedResult]()
should_[behavior]_when_[condition]()
test_[method]_[scenario]_[expected]()

Test Doubles

| Type | Purpose | When to Use | |------|---------|-------------| | Stub | Returns predefined values | Fixed API responses | | Mock | Verifies interactions | Check method called | | Fake | Simplified implementation | In-memory database | | Spy | Records calls, delegates | Partial mocking |

When to Use What

• UT: Use mocks/stubs for all external deps
• IT: Use fakes for DB, stubs for external APIs
• ST: Real components, fake only external services
• E2E: Real everything

AAA Pattern

test('method_scenario_expected', () => {
    // Arrange - Setup test data
    const input = createTestInput();
    const sut = new SystemUnderTest();

    // Act - Execute behavior
    const result = sut.execute(input);

    // Assert - Verify result
    expect(result).toBe(expected);
});

FIRST Principles

• Fast - Tests run quickly
• Independent - Tests don't affect each other
• Repeatable - Same result every time
• Self-validating - Clear pass/fail
• Timely - Written with production code

Anti-Patterns to Avoid

• ❌ Test Interdependence (tests must run in order)
• ❌ Flaky Tests (sometimes pass, sometimes fail)
• ❌ Testing Implementation Details
• ❌ Over-Mocking
• ❌ Missing Assertions
• ❌ Magic Numbers/Strings

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Configuration Detection

This skill supports project-specific configuration.

Detection Order

1. Check CONTRIBUTING.md for "Disabled Skills" section
   • If this skill is listed, it is disabled for this project
2. Check CONTRIBUTING.md for "Testing Standards" section
3. If not found, default to standard coverage targets

First-Time Setup

If no configuration found and context is unclear:

1. Ask the user: "This project hasn't configured testing standards. Would you like to customize coverage targets?"
2. After user selection, suggest documenting in CONTRIBUTING.md:

## Testing Standards

### Coverage Targets
| Metric | Target |
|--------|--------|
| Line | 80% |
| Branch | 70% |
| Function | 85% |

Configuration Example

In project's CONTRIBUTING.md:

## Testing Standards

### Coverage Targets
| Metric | Target |
|--------|--------|
| Line | 80% |
| Branch | 70% |
| Function | 85% |

### Testing Framework
- Unit Tests: Jest
- Integration Tests: Supertest
- E2E Tests: Playwright

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License: CC BY 4.0 | Source: universal-dev-standards