vitest

Vitest - 现代 TypeScript 测试

概述

Vitest 是由 Vite 驱动的新一代测试框架，专为现代 TypeScript/JavaScript 项目设计。它通过基于 HMR 的测试运行、原生 ESM 支持和一流的 TypeScript 集成，提供闪电般快速的测试执行体验。

主要功能：

• ⚡ 原生支持 Vite：基于 HMR 即时执行测试（比 Jest 快 10-100 倍）
• 🎯 TypeScript 优先：内置 TypeScript 支持，无需配置
• 🔄 原生支持 ESM：原生 ES 模块、async/await、顶层 await
• 🧪 兼容 Jest：提供兼容的 API，便于迁移
• 📸 快照测试：内置快照支持
• 🎨 组件测试：集成 React Testing Library、Vue Test Utils
• 📊 覆盖率：内置 v8/c8 覆盖率（比 Istanbul 更快）
• 🌐 UI 模式：精美的 Web UI，便于调试测试

安装：

npm install -D vitest
# TypeScript types (usually auto-detected)
npm install -D @vitest/ui  # Optional: UI mode

基本设置

1. 配置 Vitest

vitest.config.ts：

import { defineConfig } from 'vitest/config';

export default defineConfig({
  test: {
    globals: true,           // Use describe/it/expect globally
    environment: 'node',     // or 'jsdom' for DOM testing
    coverage: {
      provider: 'v8',        // or 'istanbul'
      reporter: ['text', 'json', 'html'],
      exclude: [
        'node_modules/',
        'dist/',
        '**/*.test.ts',
        '**/*.spec.ts',
      ],
    },
    include: ['**/*.{test,spec}.{ts,tsx}'],
    exclude: ['node_modules', 'dist', '.idea', '.git', '.cache'],
  },
});

2. TypeScript 配置

tsconfig.json：

{
  "compilerOptions": {
    "types": ["vitest/globals"]  // For global describe/it/expect
  }
}

替代方案（不使用全局变量）：

import { describe, it, expect } from 'vitest';

3. Package.json 脚本

{
  "scripts": {
    "test": "vitest run",              // CI mode (single run)
    "test:watch": "vitest",            // Watch mode (default)
    "test:ui": "vitest --ui",          // UI mode
    "test:coverage": "vitest run --coverage"
  }
}

核心测试模式

基本测试结构

import { describe, it, expect, beforeEach, afterEach } from 'vitest';

describe('Calculator', () => {
  let calculator: Calculator;

  beforeEach(() => {
    calculator = new Calculator();
  });

  it('adds two numbers correctly', () => {
    const result = calculator.add(2, 3);
    expect(result).toBe(5);
  });

  it('handles negative numbers', () => {
    expect(calculator.add(-5, 3)).toBe(-2);
  });
});

TypeScript 类型测试

import { describe, it, expectTypeOf, assertType } from 'vitest';

interface User {
  id: number;
  name: string;
  email: string;
}

describe('Type Safety', () => {
  it('ensures correct types', () => {
    const user: User = {
      id: 1,
      name: 'Alice',
      email: '[email protected]',
    };

    // Type assertions
    expectTypeOf(user.id).toBeNumber();
    expectTypeOf(user.name).toBeString();
    expectTypeOf(user).toMatchTypeOf<User>();

    // Assert type at compile time
    assertType<User>(user);
  });

  it('checks function return types', () => {
    function getUser(): User {
      return { id: 1, name: 'Bob', email: '[email protected]' };
    }

    expectTypeOf(getUser).returns.toMatchTypeOf<User>();
  });
});

模拟与间谍

使用 vi.mock 模拟模块

import { describe, it, expect, vi } from 'vitest';
import { fetchUser } from './api';
import { UserService } from './UserService';

// Mock entire module
vi.mock('./api', () => ({
  fetchUser: vi.fn(),
}));

describe('UserService', () => {
  it('fetches user data', async () => {
    const mockUser = { id: 1, name: 'Alice' };
    vi.mocked(fetchUser).mockResolvedValue(mockUser);

    const service = new UserService();
    const user = await service.getUser(1);

    expect(fetchUser).toHaveBeenCalledWith(1);
    expect(user).toEqual(mockUser);
  });
});

使用 vi.spyOn 监视方法

import { describe, it, expect, vi } from 'vitest';

class Logger {
  log(message: string) {
    console.log(message);
  }
}

describe('Logger Spy', () => {
  it('tracks method calls', () => {
    const logger = new Logger();
    const spy = vi.spyOn(logger, 'log');

    logger.log('Hello');
    logger.log('World');

    expect(spy).toHaveBeenCalledTimes(2);
    expect(spy).toHaveBeenCalledWith('Hello');
    expect(spy).toHaveBeenLastCalledWith('World');

    spy.mockRestore(); // Restore original implementation
  });
});

模拟实现

import { describe, it, expect, vi } from 'vitest';

describe('Mock Implementation', () => {
  it('provides custom mock implementation', () => {
    const mockFn = vi.fn((x: number) => x * 2);

    expect(mockFn(5)).toBe(10);
    expect(mockFn).toHaveBeenCalledWith(5);

    // Change implementation
    mockFn.mockImplementation((x: number) => x + 10);
    expect(mockFn(5)).toBe(15);

    // One-time implementation
    mockFn.mockImplementationOnce((x: number) => 100);
    expect(mockFn(5)).toBe(100);
    expect(mockFn(5)).toBe(15); // Back to default
  });
});

模拟计时器

import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';

describe('Timer Mocking', () => {
  beforeEach(() => {
    vi.useFakeTimers();
  });

  afterEach(() => {
    vi.restoreAllMocks();
  });

  it('fast-forwards time', () => {
    const callback = vi.fn();
    setTimeout(callback, 1000);

    vi.advanceTimersByTime(500);
    expect(callback).not.toHaveBeenCalled();

    vi.advanceTimersByTime(500);
    expect(callback).toHaveBeenCalledTimes(1);
  });

  it('runs all timers', async () => {
    const callback = vi.fn();
    setTimeout(callback, 1000);
    setTimeout(callback, 2000);

    await vi.runAllTimersAsync();
    expect(callback).toHaveBeenCalledTimes(2);
  });
});

React 测试集成

设置 React Testing Library

npm install -D @testing-library/react @testing-library/jest-dom @testing-library/user-event
npm install -D jsdom  # For DOM environment

vitest.config.ts（React）：

import { defineConfig } from 'vitest/config';
import react from '@vitejs/plugin-react';

export default defineConfig({
  plugins: [react()],
  test: {
    globals: true,
    environment: 'jsdom',
    setupFiles: './src/test/setup.ts',
  },
});

src/test/setup.ts：

import '@testing-library/jest-dom';
import { expect, afterEach } from 'vitest';
import { cleanup } from '@testing-library/react';
import * as matchers from '@testing-library/jest-dom/matchers';

expect.extend(matchers);

afterEach(() => {
  cleanup();
});

React 组件测试

import { describe, it, expect } from 'vitest';
import { render, screen } from '@testing-library/react';
import userEvent from '@testing-library/user-event';
import { Counter } from './Counter';

describe('Counter Component', () => {
  it('renders initial count', () => {
    render(<Counter initialCount={0} />);
    expect(screen.getByText('Count: 0')).toBeInTheDocument();
  });

  it('increments counter on button click', async () => {
    const user = userEvent.setup();
    render(<Counter initialCount={0} />);

    const button = screen.getByRole('button', { name: /increment/i });
    await user.click(button);

    expect(screen.getByText('Count: 1')).toBeInTheDocument();
  });

  it('calls onChange callback', async () => {
    const onChange = vi.fn();
    const user = userEvent.setup();

    render(<Counter initialCount={0} onChange={onChange} />);

    await user.click(screen.getByRole('button', { name: /increment/i }));

    expect(onChange).toHaveBeenCalledWith(1);
  });
});

测试 Hooks

import { describe, it, expect } from 'vitest';
import { renderHook, act } from '@testing-library/react';
import { useCounter } from './useCounter';

describe('useCounter Hook', () => {
  it('initializes with default value', () => {
    const { result } = renderHook(() => useCounter(0));
    expect(result.current.count).toBe(0);
  });

  it('increments counter', () => {
    const { result } = renderHook(() => useCounter(0));

    act(() => {
      result.current.increment();
    });

    expect(result.current.count).toBe(1);
  });

  it('resets counter', () => {
    const { result } = renderHook(() => useCounter(10));

    act(() => {
      result.current.reset();
    });

    expect(result.current.count).toBe(10);
  });
});

Vue 测试集成

设置 Vue Test Utils

npm install -D @vue/test-utils @vitejs/plugin-vue
npm install -D happy-dom  # Faster alternative to jsdom

vitest.config.ts（Vue）：

import { defineConfig } from 'vitest/config';
import vue from '@vitejs/plugin-vue';

export default defineConfig({
  plugins: [vue()],
  test: {
    globals: true,
    environment: 'happy-dom',
    setupFiles: './src/test/setup.ts',
  },
});

Vue 组件测试

import { describe, it, expect } from 'vitest';
import { mount } from '@vue/test-utils';
import Counter from './Counter.vue';

describe('Counter.vue', () => {
  it('renders initial count', () => {
    const wrapper = mount(Counter, {
      props: { initialCount: 5 },
    });

    expect(wrapper.text()).toContain('Count: 5');
  });

  it('increments on button click', async () => {
    const wrapper = mount(Counter, {
      props: { initialCount: 0 },
    });

    await wrapper.find('button').trigger('click');

    expect(wrapper.text()).toContain('Count: 1');
  });

  it('emits update event', async () => {
    const wrapper = mount(Counter, {
      props: { initialCount: 0 },
    });

    await wrapper.find('button').trigger('click');

    expect(wrapper.emitted('update')).toBeTruthy();
    expect(wrapper.emitted('update')?.[0]).toEqual([1]);
  });
});

异步测试

测试 Promise

import { describe, it, expect } from 'vitest';

describe('Async Operations', () => {
  it('resolves promises', async () => {
    const result = await Promise.resolve(42);
    expect(result).toBe(42);
  });

  it('rejects promises', async () => {
    await expect(Promise.reject(new Error('Failed'))).rejects.toThrow('Failed');
  });

  it('uses resolves matcher', async () => {
    await expect(Promise.resolve(42)).resolves.toBe(42);
  });
});

测试异步函数

import { describe, it, expect, vi } from 'vitest';

async function fetchData(id: number): Promise<string> {
  const response = await fetch(`/api/data/${id}`);
  return response.json();
}

describe('Async Functions', () => {
  it('fetches data successfully', async () => {
    global.fetch = vi.fn(() =>
      Promise.resolve({
        json: () => Promise.resolve('data'),
      } as Response)
    );

    const data = await fetchData(1);
    expect(data).toBe('data');
    expect(fetch).toHaveBeenCalledWith('/api/data/1');
  });

  it('handles fetch errors', async () => {
    global.fetch = vi.fn(() => Promise.reject(new Error('Network error')));

    await expect(fetchData(1)).rejects.toThrow('Network error');
  });
});

快照测试

基本快照

import { describe, it, expect } from 'vitest';
import { render } from '@testing-library/react';
import { UserCard } from './UserCard';

describe('UserCard Snapshots', () => {
  it('matches snapshot', () => {
    const { container } = render(
      <UserCard name="Alice" email="[email protected]" />
    );

    expect(container.firstChild).toMatchSnapshot();
  });

  it('matches inline snapshot', () => {
    const user = { id: 1, name: 'Bob' };
    expect(user).toMatchInlineSnapshot(`
      {
        "id": 1,
        "name": "Bob",
      }
    `);
  });
});

快照序列化器

import { describe, it, expect } from 'vitest';

expect.addSnapshotSerializer({
  test: (val) => val && typeof val.toISOString === 'function',
  print: (val) => `Date(${(val as Date).toISOString()})`,
});

describe('Custom Serializers', () => {
  it('serializes dates consistently', () => {
    const data = {
      timestamp: new Date('2024-01-01T00:00:00.000Z'),
      user: 'Alice',
    };

    expect(data).toMatchSnapshot();
  });
});

覆盖率配置

高级覆盖率设置

vitest.config.ts：

import { defineConfig } from 'vitest/config';

export default defineConfig({
  test: {
    coverage: {
      provider: 'v8',
      reporter: ['text', 'json', 'html', 'lcov'],
      reportsDirectory: './coverage',
      exclude: [
        'node_modules/',
        'dist/',
        '**/*.test.ts',
        '**/*.spec.ts',
        '**/*.config.ts',
        '**/types/',
      ],
      thresholds: {
        lines: 80,
        functions: 80,
        branches: 75,
        statements: 80,
      },
      all: true,  // Include untested files in coverage report
    },
  },
});

运行覆盖率

# Generate coverage
npx vitest run --coverage

# Coverage with UI
npx vitest --coverage --ui

# Specific threshold enforcement
npx vitest run --coverage --coverage.lines=90

从 Jest 迁移

API 兼容性

Vitest 提供兼容 Jest 的 API：

// Jest syntax works in Vitest
import { describe, it, expect, jest } from 'vitest';

// Note: Use 'vi' instead of 'jest' for new code
import { describe, it, expect, vi } from 'vitest';

// Both work, but vi is preferred
const mockFn = vi.fn();  // Preferred
const mockFn2 = jest.fn();  // Also works

迁移清单

1. 更新依赖：

npm uninstall jest @types/jest ts-jest
npm install -D vitest @vitest/ui

2. 更新 package.json：

{
  "scripts": {
    "test": "vitest run",  // Was: jest
    "test:watch": "vitest"  // Was: jest --watch
  }
}

3. 将 jest.config.js 替换为 vitest.config.ts：

// Old: jest.config.js
module.exports = {
  preset: 'ts-jest',
  testEnvironment: 'node',
};

// New: vitest.config.ts
import { defineConfig } from 'vitest/config';

export default defineConfig({
  test: {
    globals: true,
    environment: 'node',
  },
});

4. 更新测试文件：

// Change imports
- import { jest } from '@jest/globals';
+ import { vi } from 'vitest';

// Update mocks
- jest.fn()
+ vi.fn()

- jest.spyOn()
+ vi.spyOn()

- jest.mock()
+ vi.mock()

高级模式

并发测试

import { describe, it, expect } from 'vitest';

describe.concurrent('Parallel Tests', () => {
  it('test 1', async () => {
    await slowOperation();
    expect(true).toBe(true);
  });

  it('test 2', async () => {
    await slowOperation();
    expect(true).toBe(true);
  });

  // Both tests run in parallel
});

测试上下文

import { describe, it, expect, beforeEach } from 'vitest';

interface TestContext {
  user: { id: number; name: string };
  api: ApiClient;
}

describe<TestContext>('With Context', () => {
  beforeEach((context) => {
    context.user = { id: 1, name: 'Alice' };
    context.api = new ApiClient();
  });

  it<TestContext>('uses context', ({ user, api }) => {
    expect(user.name).toBe('Alice');
    expect(api).toBeDefined();
  });
});

自定义匹配器

import { expect } from 'vitest';

expect.extend({
  toBeWithinRange(received: number, floor: number, ceiling: number) {
    const pass = received >= floor && received <= ceiling;
    return {
      pass,
      message: () =>
        pass
          ? `expected ${received} not to be within range ${floor} - ${ceiling}`
          : `expected ${received} to be within range ${floor} - ${ceiling}`,
    };
  },
});

// Usage
expect(100).toBeWithinRange(90, 110);

最佳实践

1. 使用 globals: true - 导入更简单，且兼容 Jest
2. 优先使用 vi 而非 jest - 新代码使用 Vitest 原生 API
3. 使用 v8 覆盖率 - 比 Istanbul 更快，且适用于原生 ESM
4. 隔离测试 - 每项测试都应相互独立
5. 模拟外部依赖 - 网络、文件系统、计时器
6. 使用 TypeScript - 确保测试具有完整的类型安全性
7. 在 CI 模式下运行测试 - CI 中使用 vitest run，而非 watch 模式
8. 充分利用 UI 模式 - 通过可视化方式调试失败的测试
9. 使用 describe.concurrent - 并行运行相互独立的测试
10. 保持测试专注 - 尽可能让每项测试只包含一个断言

常见问题

❌ 在 CI/CD 中未使用 CI 模式：

// WRONG - watch mode hangs in CI
"test": "vitest"

// CORRECT - single run
"test": "vitest run"

✅ 正确做法：

{
  "scripts": {
    "test": "vitest run",       // CI-safe
    "test:watch": "vitest",     // Development
    "test:ui": "vitest --ui"    // Debugging
  }
}

❌ 忘记等待异步测试完成：

// WRONG - test passes before assertion
it('fetches data', () => {
  fetchData().then(data => {
    expect(data).toBeDefined();  // Never runs!
  });
});

// CORRECT
it('fetches data', async () => {
  const data = await fetchData();
  expect(data).toBeDefined();
});

❌ 未清理模拟对象：

// WRONG - mocks leak between tests
it('test 1', () => {
  vi.spyOn(console, 'log');
  // No cleanup!
});

// CORRECT
import { afterEach } from 'vitest';

afterEach(() => {
  vi.restoreAllMocks();
});

❌ 使用了错误的环境：

// WRONG - testing DOM in node environment
test: {
  environment: 'node',  // Can't test React components!
}

// CORRECT
test: {
  environment: 'jsdom',  // For React/Vue components
}

资源

• 文档：https://vitest.dev
• API 参考：https://vitest.dev/api/
• 迁移指南：https://vitest.dev/guide/migration.html
• 示例：https://github.com/vitest-dev/vitest/tree/main/examples
• UI 模式：https://vitest.dev/guide/ui.html

相关技能

使用 Vitest 时，可考虑搭配以下技能：

• typescript-core：高级 TypeScript 类型模式、tsconfig 和运行时验证
• react：集成 Testing Library 的 React 组件测试
• test-driven-development：完整的 TDD 工作流（RED/GREEN/REFACTOR 循环）

快速 TypeScript 类型模式（内联，便于独立使用）

// Type-safe test factories with generics
function createMockData<T extends Record<string, unknown>>(
  defaults: T,
  overrides?: Partial<T>
): T {
  return { ...defaults, ...overrides };
}

const mockUser = createMockData(
  { id: 1, name: 'Test', email: '[email protected]' },
  { name: 'Alice' }
);

// Runtime validation with Zod in tests
import { z } from 'zod';

const UserSchema = z.object({
  id: z.number(),
  name: z.string(),
  email: z.string().email(),
});

test('API returns valid user', async () => {
  const response = await fetch('/api/user/1');
  const data = await response.json();

  // Runtime validation + type inference
  const user = UserSchema.parse(data);
  expect(user.email).toContain('@');
});

// Const type parameters for literal inference
const createTestConfig = <const T extends Record<string, unknown>>(config: T): T => config;
const testEnv = createTestConfig({ mode: 'test', debug: false });
// Type: { mode: "test"; debug: false } (literals preserved)

快速 React 测试模式（内联，便于独立使用）

// React Testing Library with Vitest
import { render, screen, fireEvent, waitFor } from '@testing-library/react';
import { userEvent } from '@testing-library/user-event';
import { describe, test, expect, vi } from 'vitest';

// Component testing
describe('UserProfile', () => {
  test('renders user information', () => {
    const user = { id: 1, name: 'Alice', email: '[email protected]' };
    render(<UserProfile user={user} />);

    expect(screen.getByText('Alice')).toBeInTheDocument();
    expect(screen.getByText('[email protected]')).toBeInTheDocument();
  });

  test('handles form submission', async () => {
    const onSubmit = vi.fn();
    render(<UserForm onSubmit={onSubmit} />);

    const user = userEvent.setup();
    await user.type(screen.getByLabelText('Name'), 'Bob');
    await user.click(screen.getByRole('button', { name: 'Submit' }));

    await waitFor(() => {
      expect(onSubmit).toHaveBeenCalledWith({ name: 'Bob' });
    });
  });
});

// Hook testing
import { renderHook, act } from '@testing-library/react';

test('useCounter hook increments', () => {
  const { result } = renderHook(() => useCounter(0));

  expect(result.current.count).toBe(0);

  act(() => {
    result.current.increment();
  });

  expect(result.current.count).toBe(1);
});

快速 TDD 工作流参考（内联，便于独立使用）

RED → GREEN → REFACTOR 循环：

1. RED 阶段：编写失败的测试

   test('should authenticate user with valid credentials', () => {
     const user = { username: 'alice', password: 'secret123' };
     const result = authenticate(user);
     expect(result.isAuthenticated).toBe(true);
     // This fails because authenticate() doesn't exist yet
   });
   

2. GREEN 阶段：让测试通过

   function authenticate(user: User): AuthResult {
     // Minimum code to pass the test
     if (user.username === 'alice' && user.password === 'secret123') {
       return { isAuthenticated: true };
     }
     return { isAuthenticated: false };
   }
   

3. REFACTOR 阶段：改进代码

   function authenticate(user: User): AuthResult {
     // Clean up while keeping tests green
     const hashed = hashPassword(user.password);
     const storedUser = database.getUser(user.username);
     return {
       isAuthenticated: storedUser?.passwordHash === hashed
     };
   }
   

测试结构：Arrange-Act-Assert（AAA）

test('creates user successfully', async () => {
  // Arrange: Set up test data
  const userData = { username: 'alice', email: '[email protected]' };

  // Act: Perform the action
  const user = await createUser(userData);

  // Assert: Verify outcome
  expect(user.username).toBe('alice');
  expect(user.email).toBe('[email protected]');
});

Vitest 专属 TDD 功能：

// Watch mode with HMR (instant feedback)
// vitest --watch

// UI mode for visual debugging
// vitest --ui

// Run only changed tests
// vitest --changed

// Benchmark mode for performance testing
import { bench } from 'vitest';

bench('authenticate performance', () => {
  authenticate({ username: 'alice', password: 'secret' });
});

[如果一并部署，完整的 TypeScript、React 和 TDD 工作流可在相应技能中获取]

总结

• Vitest 是现代 TypeScript 测试的标准
• 通过 Vite 原生 HMR，速度比 Jest 快 10–100 倍
• ESM 优先，原生支持模块
• 兼容 Jest 的 API，便于迁移
• TypeScript 优先，内置类型支持
• 支持 React 和 Vue 的组件测试
• v8 覆盖率比 Istanbul 更快
• UI 模式便于进行可视化测试调试
• 非常适合：现代 TypeScript 项目、基于 Vite 的应用、React/Vue 组件