Test Quality Analysis

测试质量分析

Expert knowledge for analyzing and improving test quality - detecting test smells, overmocking, insufficient coverage, and testing anti-patterns.

用于分析和提升测试质量的专业知识——检测测试异味、过度Mock、覆盖率不足以及测试反模式。

Core Dimensions

核心维度

Correctness: Tests verify the right behavior
Reliability: Tests are deterministic, not flaky
Maintainability: Tests are easy to understand
Performance: Tests run quickly
Coverage: Tests cover critical code paths
Isolation: Tests don't depend on external state

正确性：测试验证正确的行为
可靠性：测试结果确定，不存在不稳定情况
可维护性：测试易于理解
性能：测试运行速度快
覆盖率：测试覆盖关键代码路径
隔离性：测试不依赖外部状态

Test Smells

测试异味

Overmocking

过度Mock

Problem: Mocking too many dependencies makes tests fragile.

typescript

// ❌ BAD: Overmocked
test('calculate total', () => {
  const mockAdd = vi.fn(() => 10)
  const mockMultiply = vi.fn(() => 20)
  // Testing implementation, not behavior
})

// ✅ GOOD: Mock only external dependencies
test('calculate order total', () => {
  const mockPricingAPI = vi.fn(() => ({ tax: 0.1 }))
  const total = calculateTotal(order, mockPricingAPI)
  expect(total).toBe(38)
})

Detection: More than 3-4 mocks, mocking pure functions, complex mock setup.

Fix: Mock only I/O boundaries (APIs, databases, filesystem).

问题：过多Mock依赖会导致测试脆弱。

typescript

// ❌ 不良示例：过度Mock
test('calculate total', () => {
  const mockAdd = vi.fn(() => 10)
  const mockMultiply = vi.fn(() => 20)
  // 测试实现细节，而非行为
})

// ✅ 良好示例：仅Mock外部依赖
test('calculate order total', () => {
  const mockPricingAPI = vi.fn(() => ({ tax: 0.1 }))
  const total = calculateTotal(order, mockPricingAPI)
  expect(total).toBe(38)
})

检测方式：存在3-4个以上的Mock、Mock纯函数、复杂的Mock配置。

修复方案：仅Mock I/O边界（API、数据库、文件系统）。

Fragile Tests

脆弱测试

Problem: Tests break with unrelated code changes.

typescript

// ❌ BAD: Tests implementation details
await page.locator('.form-container > div:nth-child(2) > button').click()

// ✅ GOOD: Semantic selector
await page.getByRole('button', { name: 'Submit' }).click()

问题：无关代码变更会导致测试失败。

typescript

// ❌ 不良示例：测试实现细节
await page.locator('.form-container > div:nth-child(2) > button').click()

// ✅ 良好示例：语义化选择器
await page.getByRole('button', { name: 'Submit' }).click()

Flaky Tests

不稳定测试

Problem: Tests pass or fail non-deterministically.

typescript

// ❌ BAD: Race condition
test('loads data', async () => {
  fetchData()
  await new Promise(resolve => setTimeout(resolve, 1000))
  expect(data).toBeDefined()
})

// ✅ GOOD: Proper async handling
test('loads data', async () => {
  const data = await fetchData()
  expect(data).toBeDefined()
})

问题：测试结果随机，时而通过时而失败。

typescript

// ❌ 不良示例：竞态条件
test('loads data', async () => {
  fetchData()
  await new Promise(resolve => setTimeout(resolve, 1000))
  expect(data).toBeDefined()
})

// ✅ 良好示例：正确处理异步
test('loads data', async () => {
  const data = await fetchData()
  expect(data).toBeDefined()
})

Poor Assertions

断言质量低下

typescript

// ❌ BAD: Weak assertion
test('returns users', async () => {
  const users = await getUsers()
  expect(users).toBeDefined() // Too vague!
})

// ✅ GOOD: Strong, specific assertions
test('creates user with correct attributes', async () => {
  const user = await createUser({ name: 'John' })
  expect(user).toMatchObject({
    id: expect.any(Number),
    name: 'John',
  })
})

typescript

// ❌ 不良示例：模糊断言
test('returns users', async () => {
  const users = await getUsers()
  expect(users).toBeDefined() // 过于模糊！
})

// ✅ 良好示例：具体明确的断言
test('creates user with correct attributes', async () => {
  const user = await createUser({ name: 'John' })
  expect(user).toMatchObject({
    id: expect.any(Number),
    name: 'John',
  })
})

Analysis Tools

分析工具

bash

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bash

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Vitest coverage (prefer bun)

Vitest 覆盖率统计（推荐使用 bun）

bun test --coverage open coverage/index.html

Check thresholds

检查阈值

bun test --coverage --coverage.thresholds.lines=80

pytest-cov (Python)

pytest-cov（Python）

uv run pytest --cov --cov-report=html open htmlcov/index.html

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uv run pytest --cov --cov-report=html open htmlcov/index.html

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Best Practices Checklist

最佳实践检查清单

Unit Test Quality (FIRST)

单元测试质量（FIRST原则）

Fast: Tests run in milliseconds
Isolated: No dependencies between tests
Repeatable: Same results every time
Self-validating: Clear pass/fail
Timely: Written alongside code

快速：测试以毫秒级运行
隔离：测试之间无依赖
可重复：每次结果一致
自验证：通过/失败结果明确
及时：与代码同步编写

Mock Guidelines

Mock 指南

Mock only external dependencies
Don't mock business logic or pure functions
Use real implementations when possible
Limit to 3-4 mocks per test maximum

仅Mock外部依赖
不要Mock业务逻辑或纯函数
尽可能使用真实实现
每个测试最多使用3-4个Mock

Coverage Goals

覆盖率目标

80%+ line coverage for business logic
100% for critical paths (auth, payment)
All error paths tested
Boundary conditions tested

业务逻辑行覆盖率达到80%以上
关键路径（认证、支付）覆盖率100%
所有错误路径均有测试覆盖
边界条件均有测试覆盖

Test Structure (AAA Pattern)

测试结构（AAA模式）

typescript

test('user registration', async () => {
  // Arrange
  const userData = { email: 'user@example.com' }

  // Act
  const user = await registerUser(userData)

  // Assert
  expect(user.email).toBe('user@example.com')
})

typescript

test('user registration', async () => {
  // 准备
  const userData = { email: 'user@example.com' }

  // 执行
  const user = await registerUser(userData)

  // 断言
  expect(user.email).toBe('user@example.com')
})

Code Review Checklist

代码评审检查清单

Tests verify behavior, not implementation
Assertions are specific and meaningful
No flaky tests (timing, ordering issues)
Proper async/await usage
Test names clearly describe behavior
Minimal code duplication
Critical paths have tests
Both happy path and error cases covered

测试验证行为而非实现细节
断言具体且有意义
不存在不稳定测试（时序、顺序问题）
正确使用 async/await
测试名称清晰描述行为
代码重复率低
关键路径有测试覆盖
覆盖正常流程和异常场景

Common Anti-Patterns

常见反模式

Testing Implementation Details

测试实现细节

typescript

// ❌ BAD
const spy = vi.spyOn(Math, 'sqrt')
calculateDistance()
expect(spy).toHaveBeenCalled() // Testing how, not what

// ✅ GOOD
const distance = calculateDistance({ x: 0, y: 0 }, { x: 3, y: 4 })
expect(distance).toBe(5) // Testing output

typescript

// ❌ 不良示例
const spy = vi.spyOn(Math, 'sqrt')
calculateDistance()
expect(spy).toHaveBeenCalled() // 测试过程，而非结果

// ✅ 良好示例
const distance = calculateDistance({ x: 0, y: 0 }, { x: 3, y: 4 })
expect(distance).toBe(5) // 测试输出结果

Mocking Too Much

过度Mock

typescript

// ❌ BAD
const mockAdd = vi.fn((a, b) => a + b)

// ✅ GOOD: Use real implementations
import { add } from './utils'
// Only mock external services
const mockPaymentGateway = vi.fn()

typescript

// ❌ 不良示例
const mockAdd = vi.fn((a, b) => a + b)

// ✅ 良好示例：使用真实实现
import { add } from './utils'
// 仅Mock外部服务
const mockPaymentGateway = vi.fn()

test-quality-analysis

Original

Translation

Test Quality Analysis

测试质量分析

Core Dimensions

核心维度

Test Smells

测试异味

Overmocking

过度Mock

Fragile Tests

脆弱测试

Flaky Tests

不稳定测试

Poor Assertions

断言质量低下

Analysis Tools

分析工具

Vitest coverage (prefer bun)

Vitest 覆盖率统计（推荐使用 bun）

Check thresholds

检查阈值

pytest-cov (Python)

pytest-cov（Python）

Best Practices Checklist

最佳实践检查清单

Unit Test Quality (FIRST)

单元测试质量（FIRST原则）

Mock Guidelines

Mock 指南

Coverage Goals

覆盖率目标

Test Structure (AAA Pattern)

测试结构（AAA模式）

Code Review Checklist

代码评审检查清单

Common Anti-Patterns

常见反模式

Testing Implementation Details

测试实现细节

Mocking Too Much

过度Mock

See Also

相关链接