testing-guide

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](./testing-pyramid.md)

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

Configuration Detection

This skill supports project-specific configuration.

Detection Order

1. Check CONTRIBUTING.md for "Disabled Skills" section
2. If this skill is listed, it is disabled for this project
3. Check CONTRIBUTING.md for "Testing Standards" section
4. 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

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