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name: testing-guide description: | Testing pyramid and test writing standards for UT/IT/ST/E2E. Use when: writing tests, discussing test coverage, test strategy, or test naming. Keywords: test, unit, integration, e2e, coverage, mock, 測試, 單元, 整合, 端對端.

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