coverage-strategist

覆盖率策略师

制定务实、注重投资回报率的测试覆盖策略。

覆盖率理念

目标：以最少的测试获得最大的信心

原则：100% 覆盖率不是目标。测试重要的部分。

关键路径识别

// Critical paths that MUST be tested
const criticalPaths = {
  authentication: {
    priority: "P0",
    coverage: "100%",
    paths: [
      "User login flow",
      "User registration",
      "Password reset",
      "Token refresh",
      "Session management",
    ],
    reasoning: "Security critical, impacts all users",
  },

  checkout: {
    priority: "P0",
    coverage: "100%",
    paths: [
      "Add to cart",
      "Update cart",
      "Apply coupon",
      "Process payment",
      "Order confirmation",
    ],
    reasoning: "Revenue critical, business essential",
  },

  dataIntegrity: {
    priority: "P0",
    coverage: "100%",
    paths: [
      "User data CRUD",
      "Order creation",
      "Inventory updates",
      "Database transactions",
    ],
    reasoning: "Data corruption would be catastrophic",
  },
};

// Important but not critical
const importantPaths = {
  userProfile: {
    priority: "P1",
    coverage: "80%",
    paths: ["Profile updates", "Avatar upload", "Preferences"],
    reasoning: "Important UX, but not business critical",
  },

  search: {
    priority: "P1",
    coverage: "70%",
    paths: ["Product search", "Filters", "Sorting"],
    reasoning: "Enhances experience, not essential",
  },
};

分层目标

# Coverage Targets by Layer

## Business Logic / Core Functions: 90-100%

**Why**: High ROI - complex logic, many edge cases
**What to test**:

- Calculations
- Validations
- State machines
- Algorithms
- Data transformations

## API Endpoints: 80-90%

**Why**: Critical integration points
**What to test**:

- Happy paths
- Error cases
- Validation
- Authentication
- Authorization

## Database Layer: 70-80%

**Why**: Data integrity matters
**What to test**:

- CRUD operations
- Transactions
- Constraints
- Migrations

## UI Components: 50-70%

**Why**: Lower ROI - visual changes, less critical
**What to test**:

- User interactions
- State changes
- Error states
- Critical flows only

## Utils/Helpers: 80-90%

**Why**: Reused everywhere, high impact
**What to test**:

- All public functions
- Edge cases
- Error handling

##「不测试」清单

// Explicit list of what NOT to test

const dontTestThese = {
  externalLibraries: {
    examples: ["React internals", "Next.js router", "Lodash functions"],
    reasoning: "Already tested by library authors",
  },

  trivialCode: {
    examples: [
      "Simple getters/setters",
      "Constants",
      "Type definitions",
      "Pass-through functions",
    ],
    reasoning: "No logic to test, waste of time",
  },

  presentationalComponents: {
    examples: ["Simple buttons", "Icons", "Layout wrappers"],
    reasoning: "Visual regression testing more appropriate",
  },

  configurationFiles: {
    examples: ["webpack.config.js", "next.config.js"],
    reasoning: "Configuration, not logic",
  },

  mockData: {
    examples: ["Fixtures", "Test data", "Storybook stories"],
    reasoning: "Not production code",
  },
};

// Example: Don't test trivial code
// ❌ Don't test this
class User {
  constructor(private name: string) {}
  getName() {
    return this.name;
  } // Trivial getter
}

// ✅ But DO test this
class User {
  constructor(private name: string) {}

  getDisplayName() {
    // Business logic
    return this.name
      .split(" ")
      .map((n) => n.charAt(0).toUpperCase() + n.slice(1))
      .join(" ");
  }
}

测试优先级矩阵

interface TestPriority {
  feature: string;
  businessImpact: "high" | "medium" | "low";
  complexity: "high" | "medium" | "low";
  changeFrequency: "high" | "medium" | "low";
  priority: "P0" | "P1" | "P2" | "P3";
  targetCoverage: string;
}

const testPriorities: TestPriority[] = [
  {
    feature: "Payment processing",
    businessImpact: "high",
    complexity: "high",
    changeFrequency: "low",
    priority: "P0",
    targetCoverage: "100%",
  },
  {
    feature: "User authentication",
    businessImpact: "high",
    complexity: "medium",
    changeFrequency: "low",
    priority: "P0",
    targetCoverage: "100%",
  },
  {
    feature: "Product search",
    businessImpact: "medium",
    complexity: "medium",
    changeFrequency: "medium",
    priority: "P1",
    targetCoverage: "80%",
  },
  {
    feature: "UI themes",
    businessImpact: "low",
    complexity: "low",
    changeFrequency: "high",
    priority: "P3",
    targetCoverage: "30%",
  },
];

// Priority calculation
function calculatePriority(
  businessImpact: number, // 1-10
  complexity: number, // 1-10
  changeFrequency: number // 1-10
): number {
  return businessImpact * 0.5 + complexity * 0.3 + changeFrequency * 0.2;
}

覆盖率配置

// jest.config.js
module.exports = {
  collectCoverageFrom: [
    "src/**/*.{ts,tsx}",
    "!src/**/*.d.ts",
    "!src/**/*.stories.tsx", // Don't count stories
    "!src/mocks/**", // Don't count mocks
    "!src/**/__tests__/**", // Don't count tests
  ],

  coverageThresholds: {
    global: {
      statements: 70,
      branches: 65,
      functions: 70,
      lines: 70,
    },
    // Critical paths: 90%+
    "./src/services/payment/**/*.ts": {
      statements: 90,
      branches: 85,
      functions: 90,
      lines: 90,
    },
    "./src/services/auth/**/*.ts": {
      statements: 90,
      branches: 85,
      functions: 90,
      lines: 90,
    },
    // Utils: 80%+
    "./src/utils/**/*.ts": {
      statements: 80,
      branches: 75,
      functions: 80,
      lines: 80,
    },
    // UI components: 50%+ (lower bar)
    "./src/components/**/*.tsx": {
      statements: 50,
      branches: 45,
      functions: 50,
      lines: 50,
    },
  },
};

测试投入的投资回报率

// Calculate ROI of testing
interface TestROI {
  feature: string;
  testingCost: number; // hours
  bugPreventionValue: number; // estimated $ saved
  roi: number; // ratio
}

const testROI: TestROI[] = [
  {
    feature: "Payment processing",
    testingCost: 40, // hours
    bugPreventionValue: 50000, // Could lose $50k revenue
    roi: 1250, // $1,250 per hour invested
  },
  {
    feature: "Authentication",
    testingCost: 20,
    bugPreventionValue: 10000, // Security breach cost
    roi: 500,
  },
  {
    feature: "Theme switcher",
    testingCost: 5,
    bugPreventionValue: 100, // Minor UX issue
    roi: 20,
  },
];

// Focus on high ROI tests
const sortedByROI = testROI.sort((a, b) => b.roi - a.roi);

务实的测试策略

# Testing Strategy Document

## Principles

1. **Business value first**: Test what breaks the business
2. **Edge cases over happy path**: Happy path is obvious
3. **Integration over unit**: Test how pieces work together
4. **Critical flows end-to-end**: User journeys matter most

## Test Types Distribution

- 70% Unit tests (fast, isolated)
- 20% Integration tests (API + DB)
- 10% E2E tests (critical flows only)

## Coverage Goals

- Overall: 70% (pragmatic goal)
- Critical business logic: 90%+
- API endpoints: 80%+
- UI components: 50%+ (user interactions only)

## What NOT to Test

- Third-party libraries
- Trivial getters/setters
- Pure presentational components
- Configuration files
- Mock data and fixtures

## Review Criteria

Before writing a test, ask:

1. What bug would this test prevent?
2. How likely is that bug?
3. How costly would that bug be?
4. Is this already covered by integration tests?

If ROI is low, skip the test.

团队指南

// Code review checklist for test coverage

const reviewChecklist = {
  criticalPath: {
    question: "Does this change affect a critical path?",
    ifYes: "MUST have comprehensive tests (90%+)",
  },

  businessLogic: {
    question: "Is this complex business logic?",
    ifYes: "MUST have unit tests with edge cases",
  },

  apiEndpoint: {
    question: "Is this a new API endpoint?",
    ifYes: "MUST have integration tests",
  },

  uiComponent: {
    question: "Is this a UI component?",
    ifYes: "Optional - test interactions only",
  },

  bugFix: {
    question: "Is this a bug fix?",
    ifYes: "MUST have regression test",
  },
};

最佳实践

1. 关注风险：测试可能出错的部分
2. 收益递减：100% 覆盖率的投资回报率较低
3. 集成测试优先于单元测试：测试行为，而非实现
4. 优先测试关键路径：支付、身份验证、数据完整性
5. 明确列出「不测试」的内容：有意决定跳过哪些测试
6. 定期审查：每季度调整目标
7. 衡量缺陷：跟踪测试是否发现了实际问题

输出检查清单

• 已识别关键路径
• 已定义分层目标
• 已创建「不测试」清单
• 已建立优先级矩阵
• 已配置覆盖率阈值
• 已完成投资回报率分析
• 已记录测试策略
• 已制定团队指南