Testing Guide Skill | Agent Skills

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

Configuration Detection

This skill supports project-specific configuration.

Detection Order

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

First-Time Setup

If no configuration found and context is unclear:

Ask the user: "This project hasn't configured testing standards. Would you like to customize coverage targets?"
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

Agent Skills: Testing Guide

Skill Files