// ❌ 测试实现细节
test('calls setState with correct value', () => {
  const spy = jest.spyOn(component, 'setState')
  component.handleClick()
  expect(spy).toHaveBeenCalledWith({ count: 1 })
})

// ✅ 测试用户可见的行为
test('increments counter when button clicked', () => {
  render(<Counter />)
  fireEvent.click(screen.getByText('+'))
  expect(screen.getByText('1')).toBeInTheDocument()
})

// ❌ 一个测试测多个行为
test('user login flow', async () => {
  // 测试表单验证
  // 测试 API 调用
  // 测试重定向
  // 测试 token 存储
})

// ✅ 拆分独立测试
test('shows error for empty email', async () => { /* ... */ })
test('shows error for invalid email format', async () => { /* ... */ })
test('calls login API with correct payload', async () => { /* ... */ })
test('redirects to dashboard on success', async () => { /* ... */ })

test('adds item to cart', () => {
  // Arrange - 准备数据
  const cart = new Cart()
  const item = { id: 1, name: 'Book', price: 29.9 }
  
  // Act - 执行操作
  cart.add(item)
  
  // Assert - 验证结果
  expect(cart.items).toHaveLength(1)
  expect(cart.total).toBe(29.9)
})

// ❌ 过度 Mock
jest.mock('@/utils/formatDate')
jest.mock('@/utils/validateEmail')
jest.mock('@/hooks/useAuth')
jest.mock('@/services/api')

// ✅ 只 Mock 外部依赖
jest.mock('@/services/api')  // 只 mock API 调用
// 纯函数直接测试，不需要 mock

describe('divide', () => {
  test('divides positive numbers', () => {
    expect(divide(10, 2)).toBe(5)
  })
  test('divides negative numbers', () => {
    expect(divide(-10, 2)).toBe(-5)
  })
  test('throws on division by zero', () => {
    expect(() => divide(10, 0)).toThrow('Cannot divide by zero')
  })
  test('handles decimal results', () => {
    expect(divide(1, 3)).toBeCloseTo(0.333, 3)
  })
})

describe('ComponentName', () => {
  // 正常路径
  describe('when data is loaded', () => {
    test('renders items', () => { /* ... */ })
  })
  
  // 加载状态
  describe('when loading', () => {
    test('shows spinner', () => { /* ... */ })
  })
  
  // 错误状态
  describe('when error occurs', () => {
    test('shows error message', () => { /* ... */ })
  })
  
  // 空状态
  describe('when no data', () => {
    test('shows empty state', () => { /* ... */ })
  })
})