測試與除錯

測試和除錯是軟體開發中不可或缺的環節。傳統IDE需要手動編寫測試用例、反覆執行測試、設定斷點、分析日誌,過程繁瑣且耗時。Claude Code透過AI輔助,讓測試和除錯變得前所未有的高效。

本文全面介紹如何用Claude Code進行智慧化的測試生成、除錯分析和效能最佳化。

執行測試

基礎測試執行

最簡單的測試執行方式是直接告訴Claude Code:

运行所有的测试

Claude Code會:

自動檢測專案使用的測試框架(Jest、Mocha、Pytest等)
執行測試命令
收集並分析測試結果
提供清晰的測試報告

I'll run all tests for this project.

🧪 Test Suite: Jest
Running tests...

Test Results:
  ✓ 124 tests passed
  ✗ 3 tests failed
  ⏱️  Total time: 2.3s

Failed Tests:
  1. UserController.createUser
     - Expected status 201, got 500
     - Error: Database connection timeout

  2. PostService.getPosts
     - Expected array length 5, got 3
     - Missing posts with status 'draft'

  3. AuthController.login
     - Token validation failed
     - JWT secret mismatch

Would you like me to investigate and fix these failures?

執行特定測試

針對特定功能的測試:

只运行用户相关的测试

Claude Code會智慧匹配相關測試:

Found 15 user-related test files:

Running user tests...
  ✓ tests/unit/user/UserModel.test.js (8/8 passed)
  ✓ tests/unit/user/UserValidator.test.js (6/6 passed)
  ✗ tests/integration/user/UserAPI.test.js (3/5 passed)
  ✓ tests/e2e/user/userFlow.test.js (4/4 passed)

Summary: 21/24 tests passed

Failed tests in UserAPI.test.js:
  - POST /api/users (email uniqueness check)
  - GET /api/users/:id (permission check)
  - DELETE /api/users/:id (soft delete)

Focus on these 3 failures?

監視模式

讓測試在程式碼變化時自動執行:

以监视模式运行测试,代码修改后自动重新测试

Claude Code會:

npm test -- --watch --coverage

並持續監控測試結果:

Watch mode enabled. Watching for file changes...

[1st run] 124 passed, 3 failed
[App.js changed] Re-running...
[2nd run] 126 passed, 1 failed
[UserService.js changed] Re-running...
[3rd run] 127 passed, 0 failed ✓

All tests passing! Real-time coverage: 87%

測試覆蓋率分析

运行测试并生成覆盖率报告

Claude Code會執行完整的覆蓋率分析:

Running tests with coverage...

📊 Coverage Report:

File                     | Lines  | Branch | Funcs  | Statements
-------------------------+--------+--------+--------+------------
src/
  controllers/
    UserController.js    |  92%   |  85%   |  100%  |    93%
    PostController.js    |  78%   |  70%   |  88%   |    80%
  services/
    UserService.js       |  95%   |  90%   |  100%  |    96%
    PostService.js       |  65%   |  50%   |  75%   |    68%  ⚠️
  models/
    User.js              |  88%   |  80%   |  100%  |    90%
    Post.js              |  85%   |  75%   |  92%   |    87%
  utils/
    validator.js         |  100%  |  100%  |  100%  |   100%  ✓

Overall Coverage         |  86%   |  78%   |  94%   |    87%

⚠️ Low coverage files:
  - PostService.js (68% statements)
    Missing: edge cases in deletePost, updatePost
    Recommendation: Add tests for error scenarios

✓ Excellent coverage:
  - validator.js (100%)
  - UserService.js (96%)

View detailed HTML report: coverage/lcov-report/index.html

生成測試用例

自動生成單元測試

Claude Code最強大的功能之一是自動生成高質量的測試用例:

为UserService.js生成完整的单元测试

Claude Code會:

分析UserService的所有方法
識別各種輸入場景
生成邊界條件測試
新增錯誤處理測試
包含Mock資料

// tests/services/UserService.test.js (自动生成)
const UserService = require('../../src/services/UserService');
const db = require('../mocks/database');

describe('UserService', () => {
  let userService;

  beforeEach(() => {
    userService = new UserService(db);
    jest.clearAllMocks();
  });

  describe('getUser', () => {
    it('should return user when valid ID is provided', async () => {
      const mockUser = { id: 1, name: 'John', email: 'john@example.com' };
      db.query.mockResolvedValue([mockUser]);

      const result = await userService.getUser(1);

      expect(result).toEqual(mockUser);
      expect(db.query).toHaveBeenCalledWith(
        'SELECT * FROM users WHERE id = 1'
      );
    });

    it('should return null when user does not exist', async () => {
      db.query.mockResolvedValue([]);

      const result = await userService.getUser(999);

      expect(result).toBeNull();
    });

    it('should handle database errors gracefully', async () => {
      db.query.mockRejectedValue(new Error('Connection timeout'));

      await expect(userService.getUser(1)).rejects.toThrow(
        'Connection timeout'
      );
    });

    it('should validate user ID parameter', async () => {
      await expect(userService.getUser(-1)).rejects.toThrow(
        'Invalid user ID'
      );

      await expect(userService.getUser('invalid')).rejects.toThrow(
        'Invalid user ID'
      );
    });
  });

  describe('createUser', () => {
    it('should create user with valid data', async () => {
      const userData = {
        name: 'Jane Doe',
        email: 'jane@example.com',
        password: 'SecurePass123'
      };

      db.execute.mockResolvedValue(123);

      const userId = await userService.createUser(userData);

      expect(userId).toBe(123);
      expect(db.execute).toHaveBeenCalledWith(
        expect.stringContaining('INSERT INTO users'),
        expect.arrayContaining(['Jane Doe', 'jane@example.com'])
      );
    });

    it('should hash password before storing', async () => {
      const userData = {
        name: 'Jane',
        email: 'jane@example.com',
        password: 'plaintext'
      };

      db.execute.mockResolvedValue(123);

      await userService.createUser(userData);

      const hashedPassword = db.execute.mock.calls[0][2][2];
      expect(hashedPassword).not.toBe('plaintext');
      expect(hashedPassword.length).toBeGreaterThan(20);
    });

    it('should validate email format', async () => {
      const invalidData = {
        name: 'Jane',
        email: 'invalid-email',
        password: 'Pass123'
      };

      await expect(userService.createUser(invalidData)).rejects.toThrow(
        'Invalid email format'
      );
    });

    it('should enforce password strength', async () => {
      const weakPasswords = [
        '123',
        'password',
        ' PASS',
        'Pass' // less than 6 chars
      ];

      for (const password of weakPasswords) {
        await expect(
          userService.createUser({
            name: 'Jane',
            email: 'jane@example.com',
            password
          })
        ).rejects.toThrow('Password does not meet requirements');
      }
    });

    it('should handle duplicate email error', async () => {
      db.execute.mockRejectedValue(
        new Error('Duplicate entry for email')
      );

      await expect(
        userService.createUser({
          name: 'Jane',
          email: 'existing@example.com',
          password: 'Pass123'
        })
      ).rejects.toThrow('Email already registered');
    });
  });

  describe('updateUser', () => {
    it('should update user fields', async () => {
      const updates = { name: 'Updated Name' };
      db.execute.mockResolvedValue(1);

      await userService.updateUser(1, updates);

      expect(db.execute).toHaveBeenCalledWith(
        expect.stringContaining('UPDATE users'),
        expect.arrayContaining(['Updated Name', 1])
      );
    });

    it('should not update sensitive fields directly', async () => {
      const updates = { password: 'newpass', id: 999 };

      await userService.updateUser(1, updates);

      // Password should be hashed separately
      // ID should not be updatable
      expect(db.execute).not.toHaveBeenCalledWith(
        expect.stringContaining('SET id ='),
        expect.anything()
      );
    });
  });

  describe('deleteUser', () => {
    it('should soft delete user', async () => {
      db.execute.mockResolvedValue(1);

      await userService.deleteUser(1);

      expect(db.execute).toHaveBeenCalledWith(
        expect.stringContaining('UPDATE users SET deleted = 1'),
        expect.arrayContaining([1])
      );
    });

    it('should return false if user not found', async () => {
      db.execute.mockResolvedValue(0);

      const result = await userService.deleteUser(999);

      expect(result).toBe(false);
    });
  });

  describe('edge cases', () => {
    it('should handle null values', async () => {
      await expect(userService.getUser(null)).rejects.toThrow();
      await expect(userService.createUser(null)).rejects.toThrow();
    });

    it('should handle SQL injection attempts', async () => {
      const maliciousData = {
        name: "'; DROP TABLE users; --",
        email: 'hacker@example.com',
        password: 'Pass123'
      };

      // Should use parameterized queries
      db.execute.mockResolvedValue(123);
      await userService.createUser(maliciousData);

      const query = db.execute.mock.calls[0][0];
      expect(query).not.toContain("'; DROP TABLE");
    });
  });
});

生成整合測試

为用户注册API生成集成测试

Claude Code會生成完整的API測試:

// tests/integration/userRegistration.test.js
const request = require('supertest');
const app = require('../../src/app');
const db = require('../../src/db');
const { generateToken } = require('../../src/utils/auth');

describe('User Registration API Integration Tests', () => {
  beforeAll(async () => {
    await db.migrate.latest();
    await db.seed.run();
  });

  afterAll(async () => {
    await db.destroy();
  });

  describe('POST /api/auth/register', () => {
    it('should register new user successfully', async () => {
      const response = await request(app)
        .post('/api/auth/register')
        .send({
          username: 'newuser',
          email: 'newuser@example.com',
          password: 'SecurePass123',
          confirmPassword: 'SecurePass123'
        })
        .expect(201);

      expect(response.body).toMatchObject({
        success: true,
        message: 'User registered successfully',
        data: {
          user: {
            id: expect.any(Number),
            username: 'newuser',
            email: 'newuser@example.com'
          },
          token: expect.any(String)
        }
      });

      expect(response.body.data.token.length).toBeGreaterThan(50);
    });

    it('should reject duplicate email', async () => {
      const userData = {
        username: 'testuser',
        email: 'existing@example.com',
        password: 'Pass123'
      };

      // First registration
      await request(app)
        .post('/api/auth/register')
        .send(userData)
        .expect(201);

      // Duplicate registration
      const response = await request(app)
        .post('/api/auth/register')
        .send(userData)
        .expect(409);

      expect(response.body).toMatchObject({
        success: false,
        error: 'Email already registered'
      });
    });

    it('should validate password confirmation', async () => {
      const response = await request(app)
        .post('/api/auth/register')
        .send({
          username: 'testuser',
          email: 'test@example.com',
          password: 'Pass123',
          confirmPassword: 'DifferentPass'
        })
        .expect(400);

      expect(response.body).toMatchObject({
        success: false,
        error: 'Passwords do not match'
      });
    });

    it('should validate required fields', async () => {
      const response = await request(app)
        .post('/api/auth/register')
        .send({
          username: 'testuser'
          // missing email and password
        })
        .expect(400);

      expect(response.body.error).toMatch(/required/);
    });

    it('should send welcome email after registration', async () => {
      const emailService = require('../../src/services/emailService');
      jest.spyOn(emailService, 'sendWelcomeEmail');

      await request(app)
        .post('/api/auth/register')
        .send({
          username: 'newuser',
          email: 'welcome@example.com',
          password: 'Pass123',
          confirmPassword: 'Pass123'
        })
        .expect(201);

      expect(emailService.sendWelcomeEmail).toHaveBeenCalledWith(
        'welcome@example.com',
        'newuser'
      );
    });

    it('should rate limit registration attempts', async () => {
      const attempts = Array(6).fill(null).map(() =>
        request(app)
          .post('/api/auth/register')
          .send({
            username: 'testuser',
            email: `test${Math.random()}@example.com`,
            password: 'Pass123'
          })
      );

      const responses = await Promise.all(attempts);

      // First 5 should succeed, 6th should be rate limited
      const successCount = responses.filter(
        r => r.status === 201
      ).length;
      const rateLimitedCount = responses.filter(
        r => r.status === 429
      ).length;

      expect(successCount).toBe(5);
      expect(rateLimitedCount).toBe(1);
    });
  });

  describe('Email Verification Flow', () => {
    it('should send verification email on registration', async () => {
      const response = await request(app)
        .post('/api/auth/register')
        .send({
          username: 'verifyuser',
          email: 'verify@example.com',
          password: 'Pass123'
        })
        .expect(201);

      // Check database for verification token
      const user = await db('users')
        .where({ email: 'verify@example.com' })
        .first();

      expect(user.verification_token).toBeDefined();
      expect(user.verified).toBe(false);
    });

    it('should verify email with valid token', async () => {
      const user = await db('users')
        .where({ email: 'verify@example.com' })
        .first();

      await request(app)
        .get(`/api/auth/verify-email?token=${user.verification_token}`)
        .expect(200);

      const verifiedUser = await db('users')
        .where({ email: 'verify@example.com' })
        .first();

      expect(verifiedUser.verified).toBe(true);
    });

    it('should reject invalid verification token', async () => {
      await request(app)
        .get('/api/auth/verify-email?token=invalid-token')
        .expect(400)
        .expect(res => {
          expect(res.body.error).toBe('Invalid verification token');
        });
    });
  });
});

生成端到端測試

为用户登录流程生成E2E测试

Claude Code可以生成完整的使用者場景測試:

// tests/e2e/loginFlow.test.js
const { chromium } = require('playwright');
const { MongoClient } = require('mongodb');

describe('User Login E2E Tests', () => {
  let browser, page, db;

  beforeAll(async () => {
    browser = await chromium.launch();
    db = await MongoClient.connect(process.env.MONGO_URI);
  });

  afterAll(async () => {
    await browser.close();
    await db.close();
  });

  beforeEach(async () => {
    page = await browser.newPage();
    await db.db('test').collection('users').deleteMany({});
  });

  it('should complete full login flow', async () => {
    // 1. Navigate to login page
    await page.goto('http://localhost:3000/login');
    await expect(page).toHaveTitle(/Login/);

    // 2. Enter credentials
    await page.fill('[name="email"]', 'test@example.com');
    await page.fill('[name="password"]', 'password123');
    await page.click('button[type="submit"]');

    // 3. Verify redirect to dashboard
    await expect(page).toHaveURL('http://localhost:3000/dashboard');

    // 4. Verify user is logged in
    const username = await page.textContent('[data-testid="user-name"]');
    expect(username).toBe('Test User');

    // 5. Verify JWT token is stored
    const cookies = await page.context().cookies();
    const tokenCookie = cookies.find(c => c.name === 'auth_token');
    expect(tokenCookie).toBeDefined();
    expect(tokenCookie.value.length).toBeGreaterThan(50);
  });

  it('should show error for invalid credentials', async () => {
    await page.goto('http://localhost:3000/login');

    await page.fill('[name="email"]', 'wrong@example.com');
    await page.fill('[name="password"]', 'wrongpass');
    await page.click('button[type="submit"]');

    // Should stay on login page
    await expect(page).toHaveURL('http://localhost:3000/login');

    // Should show error message
    const error = await page.textContent('[data-testid="login-error"]');
    expect(error).toBe('Invalid email or password');
  });

  it('should remember me functionality', async () => {
    await page.goto('http://localhost:3000/login');

    await page.fill('[name="email"]', 'test@example.com');
    await page.fill('[name="password"]', 'password123');
    await page.check('[name="remember"]');
    await page.click('button[type="submit"]');

    // Check remember me cookie
    const cookies = await page.context().cookies();
    const rememberMeCookie = cookies.find(
      c => c.name === 'remember_me'
    );

    expect(rememberMeCookie).toBeDefined();
    expect(rememberMeCookie.expires).toBeGreaterThan(Date.now() / 1000);
  });

  it('should redirect authenticated user to dashboard', async () => {
    // First login
    await page.goto('http://localhost:3000/login');
    await page.fill('[name="email"]', 'test@example.com');
    await page.fill('[name="password"]', 'password123');
    await page.click('button[type="submit"]');

    await expect(page).toHaveURL('http://localhost:3000/dashboard');

    // Logout
    await page.click('[data-testid="logout-button"]');

    // Try to access login page while authenticated
    await page.goto('http://localhost:3000/login');

    // Should redirect to dashboard
    await expect(page).toHaveURL('http://localhost:3000/dashboard');
  });

  it('should handle password reset flow', async () => {
    await page.goto('http://localhost:3000/login');

    // Click forgot password
    await page.click('a[href="/forgot-password"]');

    await expect(page).toHaveURL('http://localhost:3000/forgot-password');

    // Enter email
    await page.fill('[name="email"]', 'test@example.com');
    await page.click('button[type="submit"]');

    // Should show success message
    const success = await page.textContent('[data-testid="reset-success"]');
    expect(success).toContain('Password reset email sent');

    // Check database for reset token
    const user = await db.db('test').collection('users').findOne({
      email: 'test@example.com'
    });

    expect(user.resetPasswordToken).toBeDefined();
  });
});

對比傳統方式

傳統測試編寫方式:

手動分析程式碼邏輯
思考需要測試的場景
編寫測試程式碼
建立Mock資料
執行並除錯測試
修復測試問題
耗時: 30分鐘-2小時/檔案

Claude Code方式:

为OrderController生成完整的测试用例,包括:
- 正常流程
- 错误处理
- 边界条件
- 权限验证
- 性能测试

時間: 1-3分鐘,而且測試覆蓋更全面。

除錯程式碼

智慧錯誤分析

當程式碼出現問題時,直接告訴Claude Code:

我的登录功能有问题,用户报告无法登录

Claude Code會:

檢視相關的程式碼檔案
分析可能的問題點
檢查日誌檔案
提供診斷和建議

I'll investigate the login issue.

🔍 Analyzing login functionality...

Found 3 files related to login:
  - src/controllers/AuthController.js
  - src/services/AuthService.js
  - src/models/User.js

📋 Potential Issues Detected:

1. ⚠️ In AuthController.js (line 45):
   - Issue: Comparing password using === instead of bcrypt.compare
   - Impact: Passwords will never match (stored as hash, compared as plain text)
   - Severity: CRITICAL

   Code:
     if (user.password === password) {  // ❌ Wrong
       return { success: true };
     }

   Should be:
     if (await bcrypt.compare(password, user.password)) {  // ✓ Correct
       return { success: true };
     }

2. ⚠️ In AuthService.js (line 23):
   - Issue: Missing error handling for database timeouts
   - Impact: App crashes when DB is slow
   - Severity: HIGH

3. ⚠️ In User model (line 67):
   - Issue: Email case sensitivity not handled
   - Impact: User@example.com and user@example.com treated as different
   - Severity: MEDIUM

Would you like me to fix these issues?

日誌分析

Claude Code可以分析日誌檔案找出問題:

分析logs/error.log中的错误

Claude Code會智慧解析日誌:

📊 Analyzing logs/error.log...

Log Summary:
  - Total errors: 234
  - Time range: 2024-01-15 to 2024-01-22
  - Most affected endpoint: /api/payments/process

🔥 Top Errors:

1. Database Connection Timeout (127 occurrences)
   Pattern: "Error: Connection timeout after 30000ms"
   First seen: 2024-01-18 14:23:11
   Last seen: 2024-01-22 09:45:33
   Most frequent times: 9:00-11:00 AM (peak hours)

   Root Cause Analysis:
   - Database connection pool size: 10 (too small)
   - Query timeout: 30s (too long)
   - No connection retry logic

   Recommended Fix:
   ```javascript
   // Increase pool size
   pool: {
     min: 5,
     max: 50,  // was 10
     acquireTimeout: 10000,  // was 30000
     idle: 5000
   }

   // Add retry logic
   async function queryWithRetry(sql, retries = 3) {
     for (let i = 0; i < retries; i++) {
       try {
         return await db.query(sql);
       } catch (err) {
         if (i === retries - 1) throw err;
         await sleep(1000 * (i + 1));  // exponential backoff
       }
     }
   }

JWT Token Expired (45 occurrences) Pattern: "JsonWebTokenError: jwt expired" Mostly from: mobile app users

Analysis:
- Token expiry: 1 hour (too short for mobile)
- No refresh token mechanism
- No auto-refresh on client
Recommendation:
```
// Implement refresh tokens
const accessToken = jwt.sign({ userId }, SECRET, { expiresIn: '15m' });
const refreshToken = jwt.sign({ userId }, REFRESH_SECRET, {
  expiresIn: '7d'
});
```

Payment Gateway Timeout (38 occurrences) Pattern: "ETIMEDOUT connecting to payment API" Endpoint: POST /api/payments/process

Issues:

No timeout handling
No fallback payment gateway
Transactions left in 'pending' state

Fix:

try {
  const result = await paymentGateway.charge(amount);
  await updateTransactionStatus(txId, 'completed');
} catch (err) {
  if (err.code === 'ETIMEDOUT') {
    // Check payment status later
    await scheduleStatusCheck(txId);
    await updateTransactionStatus(txId, 'pending_confirmation');
  }
}

Unhandled Promise Rejection (12 occurrences) Pattern: "UnhandledPromiseRejectionWarning"

Files affected:
- src/services/NotificationService.js (line 89)
- src/controllers/WebhookController.js (line 45)
Add error handling:
```
process.on('unhandledRejection', (reason, promise) => {
  logger.error('Unhandled Rejection at:', promise, 'reason:', reason);
});
```

📈 Error Trends:

Daily average: 33 errors/day
Increasing trend: +15% over last week
Critical errors need immediate attention

Would you like me to implement these fixes?

### 效能瓶頸分析

分析为什么我的API响应这么慢

Claude Code會進行效能分析:

⏱️ Performance Analysis Report

Testing endpoint: GET /api/posts (with 10000 records)

Current Performance:

Average response time: 2.3s
P50: 1.8s
P95: 4.2s
P99: 6.1s
Max: 8.7s

🐌 Performance Bottlenecks Identified:

N+1 Query Problem (Impact: 60% of slowness) Location: PostController.getPosts()

Issue: For each post, making separate query to get author info:

// ❌ Bad: N+1 queries
const posts = await db.query('SELECT * FROM posts');
for (const post of posts) {
  post.author = await db.query(
    'SELECT * FROM users WHERE id = ?',
    [post.author_id]  // Separate query for each post!
  );
}

Fix:

// ✓ Good: Single query with JOIN
const posts = await db.query(`
  SELECT
    posts.*,
    users.name as author_name,
    users.email as author_email
  FROM posts
  LEFT JOIN users ON posts.author_id = users.id
`);

Expected improvement: 2.3s → 0.4s (82% faster)

Missing Index (Impact: 25% of slowness) Location: posts.title, posts.status

Analysis:
- Query filtering by status: 120ms (should be under 5ms)
- Full table scan on every request
Solution:
```
CREATE INDEX idx_posts_status ON posts(status);
CREATE INDEX idx_posts_created_at ON posts(created_at DESC);
CREATE INDEX idx_posts_author_id ON posts(author_id);
```
Expected improvement: Additional 25% speed boost

No Caching (Impact: 10% of slowness) Popular posts queried repeatedly

Solution:

const cacheKey = 'posts:popular';
let posts = await redis.get(cacheKey);

if (!posts) {
  posts = await db.query('SELECT * FROM posts ORDER BY views DESC LIMIT 10');
  await redis.setex(cacheKey, 300, JSON.stringify(posts));  // Cache for 5 min
}

return JSON.parse(posts);

Over-fetching Data (Impact: 5% of slowness) Fetching all columns when only need some

Before:

SELECT * FROM posts  // Returns 15 columns

After:

SELECT id, title, excerpt, author_id, created_at
FROM posts  // Only 5 columns

📊 Expected Results After Fixes:

Metric | Before | After | Improvement ----------------+---------+---------+------------- Average | 2.3s | 0.3s | 87% faster P95 | 4.2s | 0.5s | 88% faster P99 | 6.1s | 0.7s | 89% faster Database load | 100% | 15% | 85% reduction Memory usage | 450MB | 120MB | 73% reduction

💡 Additional Recommendations:

Implement pagination for large datasets
Add response compression (gzip)
Use CDN for static assets
Enable HTTP/2
Consider read replicas for scaling

Would you like me to implement these optimizations?

### 記憶體洩漏檢測

检查我的应用是否有内存泄漏

Claude Code會分析記憶體使用模式:

🔍 Memory Leak Detection Report

Monitoring memory usage over 1 hour...

📊 Memory Usage Pattern: Initial: 85 MB After 100 requests: 145 MB After 1000 requests: 380 MB After 10000 requests: 1.2 GB

⚠️ SUSPICIOUS: Memory grows linearly with requests Growth rate: ~110 KB per request This indicates a memory leak!

🐛 Leak Sources Identified:

Event Listeners Not Removed (40% of leaks) Location: src/components/ChatWidget.jsx

Issue:

// ❌ Bad: Listeners accumulate
useEffect(() => {
  window.addEventListener('resize', handleResize);
  window.addEventListener('scroll', handleScroll);
  // No cleanup function!
}, []);

Fix:

// ✓ Good: Cleanup listeners
useEffect(() => {
  window.addEventListener('resize', handleResize);
  window.addEventListener('scroll', handleScroll);

  return () => {
    window.removeEventListener('resize', handleResize);
    window.removeEventListener('scroll', handleScroll);
  };
}, []);

Unclosed Database Connections (30% of leaks) Location: src/services/DatabaseService.js

Issue:

// ❌ Bad: Connections never closed
async function query(sql) {
  const conn = await pool.getConnection();
  return conn.query(sql);
  // conn.release() never called!
}

Fix:

// ✓ Good: Always release
async function query(sql) {
  const conn = await pool.getConnection();
  try {
    return await conn.query(sql);
  } finally {
    conn.release();  // Always release, even on error
  }
}

Growing Cache Without Eviction (20% of leaks) Location: src/utils/cache.js

Issue:

// ❌ Bad: Infinite cache growth
const cache = new Map();

function set(key, value) {
  cache.set(key, value);  // Never removes old entries
}

Fix:

// ✓ Good: LRU cache with max size
const LRU = require('lru-cache');
const cache = new LRU({
  max: 500,  // Max 500 entries
  ttl: 1000 * 60 * 5  // Expire after 5 min
});

Timers Not Cleared (10% of leaks) Location: src/services/PollingService.js

Issue:

// ❌ Bad: Timers accumulate
function startPolling() {
  setInterval(() => {
    fetchData();
  }, 1000);
  // Interval ID not saved, can't be cleared
}

Fix:

// ✓ Good: Track and clear
const intervals = new Set();

function startPolling() {
  const id = setInterval(() => fetchData(), 1000);
  intervals.add(id);
}

function stopPolling() {
  intervals.forEach(id => clearInterval(id));
  intervals.clear();
}

🧪 Verification Steps:

Take heap snapshot before:
```
node --heap-prof snapshot.js
```

Run load test:

ab -n 10000 -c 100 http://localhost:3000/api/posts

Take heap snapshot after

Compare snapshots:

Before: 85 MB
After: 95 MB  ✓ (acceptable growth)

Would you like me to implement these fixes and verify the memory leaks are resolved?

### 實時除錯協助

在開發過程中遇到bug時:

我正在调试这个问题: 当用户点击"保存"按钮时,数据没有保存到数据库

測試覆蓋率提升

覆蓋率分析

分析测试覆盖率,找出未测试的代码

Claude Code會深入分析覆蓋率:

📊 Test Coverage Analysis

Running tests with coverage...

Current Coverage: 72%

🔍 Uncovered Code Analysis:

1. src/controllers/PaymentController.js (45% covered)

   ❌ Untested lines:
     89-124: processPayment() error handling
     156-189: refundPayment() edge cases
     201-234: handleWebhook() webhook types

   Missing scenarios:
     - Payment gateway timeout
     - Invalid payment amount
     - Refund for non-existent transaction
     - Partial refunds
     - Webhook signature verification
     - Duplicate webhook handling

   Recommended tests:
     ```javascript
     describe('Payment error handling', () => {
       it('should handle gateway timeout', async () => {
         mockGateway.charge.mockRejectedValue(
           new Error('ETIMEDOUT')
         );

         await expect(
           controller.processPayment(invalidAmount)
         ).rejects.toThrow('Payment timeout');

         // Verify transaction status
         expect(transaction.status).toBe('timeout');
       });

       it('should handle negative amounts', async () => {
         await expect(
           controller.processPayment({ amount: -50 })
         ).rejects.toThrow(
           ValidationError,
           'Amount must be positive'
         );
       });

       it('should process partial refunds', async () => {
         const payment = await createPayment({ amount: 100 });

         const refund = await controller.refundPayment({
           transactionId: payment.id,
           amount: 30  // Partial refund
         });

         expect(refund.refundAmount).toBe(30);
         expect(refund.originalAmount).toBe(100);
       });

       it('should verify webhook signatures', async () => {
         const webhook = {
           type: 'payment.succeeded',
           signature: 'invalid_signature',
           data: { ... }
         };

         await expect(
           controller.handleWebhook(webhook)
         ).rejects.toThrow('Invalid webhook signature');
       });
     });

src/services/EmailService.js (60% covered)

❌ Untested branches:

Email sending retry logic
Template rendering with missing variables
Attachment handling
Batch email sending
Unsubscribe link generation

Critical missing tests:

describe('Email sending retries', () => {
  it('should retry on transient failures', async () => {
    let attempts = 0;
    mockTransporter.sendMail.mockImplementation(() => {
      attempts++;
      if (attempts < 3) {
        throw new Error('ETIMEDOUT');
      }
      return Promise.resolve({ messageId: '123' });
    });

    await emailService.send(options);

    expect(attempts).toBe(3);  // Retried twice
  });

  it('should give up after max retries', async () => {
    mockTransporter.sendMail.mockRejectedValue(
      new Error('Permanent failure')
    );

    await expect(
      emailService.send(options)
    ).rejects.toThrow('Permanent failure');

    expect(mockTransporter.sendMail).toHaveBeenCalledTimes(3);
  });
});

src/utils/validator.js (85% covered)

⚠️ Partial coverage:

Complex validation rules not tested
Custom validator functions not covered

Missing edge cases:

describe('Complex validation', () => {
  it('should validate nested objects', () => {
    const data = {
      user: {
        profile: {
          age: '25',  // String, should be number
          address: {
            zip: '123'  // Invalid format
          }
        }
      }
    };

    const result = validator.validate(data, schema);
    expect(result.errors).toHaveLength(2);
  });

  it('should handle conditional validation', () => {
    const schema = {
      type: 'object',
      if: { properties: { accountType: { const: 'business' } } },
      then: {
        required: ['taxId', 'companyName']
      }
    };

    const personalAccount = { accountType: 'personal' };
    expect(
      validator.validate(personalAccount, schema).valid
    ).toBe(true);

    const businessAccount = { accountType: 'business' };
    expect(
      validator.validate(businessAccount, schema).valid
    ).toBe(false);
  });
});

src/middleware/auth.js (50% covered)

❌ Untested scenarios:

Token expiration edge cases
Refresh token rotation
Multi-device logout
Permission inheritance
Role hierarchy

Critical tests needed:

describe('Token expiration', () => {
  it('should reject expired token', async () => {
    const expiredToken = jwt.sign(
      { userId: 123 },
      SECRET,
      { expiresIn: '-1h' }  // Expired
    );

    const response = await request(app)
      .get('/api/protected')
      .set('Authorization', `Bearer ${expiredToken}`)
      .expect(401);

    expect(response.body.error).toContain('expired');
  });

  it('should handle token expiration grace period', async () => {
    const token = jwt.sign(
      { userId: 123 },
      SECRET,
      { expiresIn: '5s' }
    );

    // Wait for token to expire
    await sleep(6000);

    // Should still work due to grace period
    const response = await request(app)
      .get('/api/protected')
      .set('Authorization', `Bearer ${token}`)
      .expect(200);
  });
});

📈 Coverage Improvement Plan:

Priority 1 (Critical):

Payment error handling: +25% coverage
Auth token refresh: +15% coverage
Email retries: +10% coverage

Priority 2 (Important):

Webhook handling: +12% coverage
Complex validation: +8% coverage
Permission checks: +10% coverage

Priority 3 (Nice to have):

Edge cases: +10% coverage
Error boundaries: +5% coverage

Target: 72% → 90% (+18%)

Would you like me to generate the missing tests?

### 邊界條件測試

为用户注册添加边界条件测试

Claude Code會生成全面的邊界測試:

```javascript
// tests/registration/edgeCases.test.js

describe('User Registration - Edge Cases', () => {
  describe('Input validation boundaries', () => {
    it('should accept minimum valid password length', async () => {
      const response = await request(app)
        .post('/api/auth/register')
        .send({
          email: 'test@example.com',
          password: 'abc123'  // Exactly 6 chars
        })
        .expect(201);

      expect(response.body.data.user.id).toBeDefined();
    });

    it('should reject password just below minimum', async () => {
      await request(app)
        .post('/api/auth/register')
        .send({
          email: 'test@example.com',
          password: 'abc12'  // 5 chars
        })
        .expect(400);
    });

    it('should accept maximum valid username length', async () => {
      const longUsername = 'a'.repeat(50);  // Max length

      const response = await request(app)
        .post('/api/auth/register')
        .send({
          username: longUsername,
          email: 'test@example.com',
          password: 'password123'
        })
        .expect(201);
    });

    it('should reject username exceeding maximum', async () => {
      const tooLongUsername = 'a'.repeat(51);

      await request(app)
        .post('/api/auth/register')
        .send({
          username: tooLongUsername,
          email: 'test@example.com',
          password: 'password123'
        })
        .expect(400);
    });

    it('should handle empty strings', async () => {
      await request(app)
        .post('/api/auth/register')
        .send({
          username: '',  // Empty
          email: 'test@example.com',
          password: 'password123'
        })
        .expect(400);
    });

    it('should handle whitespace-only values', async () => {
      await request(app)
        .post('/api/auth/register')
        .send({
          username: '   ',  // Only spaces
          email: 'test@example.com',
          password: 'password123'
        })
        .expect(400);
    });
  });

  describe('Email format edge cases', () => {
    const invalidEmails = [
      'plainaddress',
      '@missingusername.com',
      'username@',
      'username@.com',
      'username@domain.',
      '.username@yahoo.com',
      'username@yahoo.com.',
      'username@yahoo..com',
      'username@yahoo@.com',
      'username@yahoo.c',
      'username@yahoo.corporate'
    ];

    it.each(invalidEmails)('should reject invalid email: %s', async (email) => {
      await request(app)
        .post('/api/auth/register')
        .send({
          email,
          password: 'password123'
        })
        .expect(400);
    });

    it('should handle email with special characters', async () => {
      const validSpecialChars = [
        'user+tag@example.com',
        'user.name@example.com',
        'user_name@example.com',
        'user-name@example.com'
      ];

      for (const email of validSpecialChars) {
        await request(app)
          .post('/api/auth/register')
          .send({
            email,
            password: 'password123'
          })
          .expect(201);
      }
    });

    it('should handle international email addresses', async () => {
      const internationalEmails = [
        '用户@例子.广告',
        'उपयोगकर्ता@उदाहरण.परीक्षा',
        'user@example.中国'
      ];

      for (const email of internationalEmails) {
        await request(app)
          .post('/api/auth/register')
          .send({
            email,
            password: 'password123'
          })
          .expect(201);
      }
    });
  });

  describe('Password complexity edge cases', () => {
    it('should enforce uppercase requirement', async () => {
      await request(app)
        .post('/api/auth/register')
        .send({
          email: 'test@example.com',
          password: 'lowercase123'
        })
        .expect(400);
    });

    it('should enforce lowercase requirement', async () => {
      await request(app)
        .post('/api/auth/register')
        .send({
          email: 'test@example.com',
          password: 'UPPERCASE123'
        })
        .expect(400);
    });

    it('should enforce number requirement', async () => {
      await request(app)
        .post('/api/auth/register')
        .send({
          email: 'test@example.com',
          password: 'NoNumbers'
        })
        .expect(400);
    });

    it('should handle password with only special chars', async () => {
      await request(app)
        .post('/api/auth/register')
        .send({
          email: 'test@example.com',
          password: '!@#$%^&*()'
        })
        .expect(400);
    });

    it('should handle password with common patterns', async () => {
      const commonPasswords = [
        'Password123',
        '12345678',
        'qwerty123',
        'admin123',
        'letmein123'
      ];

      for (const password of commonPasswords) {
        await request(app)
          .post('/api/auth/register')
          .send({
            email: 'test@example.com',
            password
          })
          .expect(400);  // Should reject common passwords
      }
    });
  });

  describe('Concurrent registration edge cases', () => {
    it('should handle simultaneous duplicate registrations', async () => {
      const userData = {
        email: 'concurrent@example.com',
        password: 'Password123'
      };

      // Send 10 identical requests simultaneously
      const requests = Array(10).fill(null).map(() =>
        request(app)
          .post('/api/auth/register')
          .send(userData)
      );

      const responses = await Promise.all(requests);

      // Only one should succeed
      const successes = responses.filter(r => r.status === 201);
      const conflicts = responses.filter(r => r.status === 409);

      expect(successes).toHaveLength(1);
      expect(conflicts).toHaveLength(9);
    });

    it('should handle rapid sequential registrations', async () => {
      const requests = [];

      // Send 100 requests as fast as possible
      for (let i = 0; i < 100; i++) {
        requests.push(
          request(app)
            .post('/api/auth/register')
            .send({
              email: `user${i}@example.com`,
              password: 'Password123'
            })
        );
      }

      const responses = await Promise.all(requests);
      const successes = responses.filter(r => r.status === 201);

      // All should succeed (different emails)
      expect(successes).toHaveLength(100);
    });
  });

  describe('Database edge cases', () => {
    it('should handle database connection loss', async () => {
      // Simulate DB disconnect
      await db.disconnect();

      const response = await request(app)
        .post('/api/auth/register')
        .send({
          email: 'test@example.com',
          password: 'Password123'
        })
        .expect(503);

      expect(response.body.error).toContain('Database unavailable');

      // Reconnect
      await db.connect();
    });

    it('should handle transaction rollback on error', async () => {
      // Mock DB error in middle of transaction
      db.transaction.mockImplementationOnce(async (callback) => {
        await callback();
        throw new Error('Transaction failed');
      });

      await request(app)
        .post('/api/auth/register')
        .send({
          email: 'test@example.com',
          password: 'Password123'
        })
        .expect(500);

      // Verify user was not created
      const user = await db.users.findOne({ email: 'test@example.com' });
      expect(user).toBeNull();
    });
  });

  describe('Security edge cases', () => {
    it('should sanitize HTML in username', async () => {
      const response = await request(app)
        .post('/api/auth/register')
        .send({
          username: '<script>alert("xss")</script>',
          email: 'test@example.com',
          password: 'Password123'
        })
        .expect(201);

      // Should be escaped
      expect(response.body.data.user.username).not.toContain('<script>');
    });

    it('should prevent SQL injection in email', async () => {
      const maliciousEmail = "'; DROP TABLE users; --";

      await request(app)
        .post('/api/auth/register')
        .send({
          email: maliciousEmail,
          password: 'Password123'
        })
        .expect(400);  // Should be rejected by validation

      // Verify users table still exists
      const users = await db.users.find();
      expect(Array.isArray(users)).toBe(true);
    });

    it('should rate limit repeated failed attempts', async () => {
      const requests = Array(20).fill(null).map(() =>
        request(app)
          .post('/api/auth/register')
          .send({
            email: 'existing@example.com',  // Will fail (duplicate)
            password: 'Password123'
          })
      );

      const responses = await Promise.all(requests);
      const rateLimited = responses.filter(r => r.status === 429);

      expect(rateLimited.length).toBeGreaterThan(0);
    });
  });
});

實用技巧和最佳實踐

測試技巧

1. 使用測試工廠模式

// tests/factories/userFactory.js
class UserFactory {
  static create(overrides = {}) {
    return {
      username: faker.internet.userName(),
      email: faker.internet.email(),
      password: 'SecurePass123',
      role: 'user',
      ...overrides
    };
  }

  static async createInDb(overrides = {}) {
    const userData = this.create(overrides);
    return await User.create(userData);
  }
}

// Usage in tests
const user = await UserFactory.createInDb({ role: 'admin' });

2. 使用固定裝置(Fixtures)

// tests/fixtures/users.json
{
  "standardUser": {
    "email": "user@example.com",
    "password": "Password123",
    "role": "user"
  },
  "adminUser": {
    "email": "admin@example.com",
    "password": "AdminPass123",
    "role": "admin"
  }
}

// Load fixtures in tests
const fixtures = require('../fixtures/users');
const admin = await User.create(fixtures.adminUser);

3. 使用快照測試

it('should match snapshot for user profile', () => {
  const profile = generateProfile(user);
  expect(profile).toMatchSnapshot();
});

// Update snapshots when API changes intentionally
// npm test -- -u

4. 測試隔離

beforeEach(async () => {
  // Clean database before each test
  await db.truncateAll();
});

afterEach(async () => {
  // Clear mocks
  jest.clearAllMocks();
});

除錯技巧

1. 使用條件斷點

// Instead of:
console.log('Debug:', user);

// Use:
if (user.id === 12345) {  // Only log for specific user
  console.log('Debug:', user);
}

2. 結構化日誌

// Bad
console.log('User created:', user);

// Good
logger.info('User created', {
  userId: user.id,
  email: user.email,
  timestamp: Date.now(),
  source: 'UserController.createUser'
});

3. 錯誤堆疊追蹤

function enhanceError(error, context) {
  error.context = context;
  error.timestamp = new Date().toISOString();
  Error.captureStackTrace(error, enhanceError);
  return error;
}

try {
  await riskyOperation();
} catch (error) {
  throw enhanceError(error, {
    operation: 'riskyOperation',
    userId: req.user.id
  });
}

4. 效能監控

function measurePerformance(fn) {
  return async (...args) => {
    const start = Date.now();
    const memoryBefore = process.memoryUsage().heapUsed;

    try {
      return await fn(...args);
    } finally {
      const duration = Date.now() - start;
      const memoryUsed = process.memoryUsage().heapUsed - memoryBefore;

      logger.info('Performance:', {
        function: fn.name,
        duration: `${duration}ms`,
        memory: `${Math.round(memoryUsed / 1024 / 1024)}MB`
      });
    }
  };
}

// Usage
const processData = measurePerformance(async (data) => {
  // Heavy computation
});