从TDD走到ATDD：测试驱动开发笔记

// 以前的开发方式：先写代码，再写测试
function calculateTotal(items) {
  return items.reduce((sum, item) => sum + item.price, 0);
}

// 然后写测试
test('calculateTotal should sum prices', () => {
  const items = [
    { price: 10 },
    { price: 20 },
    { price: 30 }
  ];
  
  expect(calculateTotal(items)).toBe(60);
});

// Red-Green-Refactor

// 1. Red：写一个失败的测试
test('calculateTotal with empty array should return 0', () => {
  expect(calculateTotal([])).toBe(0);
});

// 运行测试，失败（函数还没写）

// 2. Green：让测试通过
function calculateTotal(items) {
  if (items.length === 0) return 0;
  return items.reduce((sum, item) => sum + item.price, 0);
}

// 运行测试，通过

// 3. Refactor：重构代码，保持测试通过
function calculateTotal(items) {
  return items.reduce((sum, item) => sum + item.price, 0);
}

// 场景：用户注册功能

// Red 1
test('should create user with valid data', () => {
  const userData = {
    name: 'Alice',
    email: '[email protected]',
    password: 'secure123'
  };
  
  const user = userService.register(userData);
  
  expect(user.id).toBeDefined();
  expect(user.name).toBe(userData.name);
});

// Green 1
class UserService {
  register(userData) {
    const user = {
      id: Date.now(),
      ...userData
    };
    return user;
  }
}

// Red 2：验证邮箱格式
test('should throw error for invalid email', () => {
  const userData = {
    name: 'Alice',
    email: 'invalid-email',
    password: 'secure123'
  };
  
  expect(() => userService.register(userData)).toThrow('Invalid email');
});

// Green 2
class UserService {
  register(userData) {
    this.validateEmail(userData.email);
    this.validatePassword(userData.password);
    
    const user = {
      id: Date.now(),
      ...userData
    };
    return user;
  }
  
  validateEmail(email) {
    if (!/^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(email)) {
      throw new Error('Invalid email');
    }
  }
  
  validatePassword(password) {
    if (password.length < 8) {
      throw new Error('Password too short');
    }
  }
}

// Acceptance Test-Driven Development

// 1. 定义验收标准
// Feature: 用户注册
//   用户应该能够使用有效的邮箱和密码注册账户
//   用户不应该能够使用无效的邮箱注册账户
//   密码应该至少 8 个字符

// 2. 编写验收测试
const { Given, When, Then } = require('cucumber');

Given('a user with valid registration data', function () {
  this.userData = {
    name: 'Alice',
    email: '[email protected]',
    password: 'secure12345'
  };
});

When('the user attempts to register', function () {
  this.result = userService.register(this.userData);
});

Then('the user should be created successfully', function () {
  expect(this.result.id).toBeDefined();
});

Given('a user with invalid email', function () {
  this.userData = {
    name: 'Alice',
    email: 'invalid-email',
    password: 'secure12345'
  };
});

Then('registration should fail', function () {
  expect(() => userService.register(this.userData)).toThrow();
});

// 不好的测试
test('true should be true', () => {
  expect(true).toBe(true);
});

// 好的测试
test('should handle empty cart checkout', () => {
  const cart = createEmptyCart();
  
  expect(() => checkout(cart)).toThrow('Cart is empty');
});

// 简化测试
test('should calculate order total correctly', () => {
  const order = createOrder([
    { name: 'Item 1', price: 10, quantity: 2 }
  ]);
  
  expect(order.getTotal()).toBe(20);
});

// 从小范围开始
// 1. 在新功能中尝试 TDD
// 2. 在重构中尝试 TDD
// 3. 逐步扩展到整个项目