all-in-kingsoft/hhs/REACT/5. 工程实践篇/16-测试.md

---
tags: [React, Testing, Vitest, RTL, Frontend]
create time: 2026-04-29 22:15
---

# 测试

## 概述

可靠的测试是大型 React 项目长期维护的基石。本文档以 Vitest + React Testing Library (RTL) 为主，介绍组件单元测试、Hook 测试和集成测试的最佳实践。

## 测试金字塔

```mermaid
graph TB
    A["测试金字塔"]
    
    A --> B["单元测试 ~70%"]
    A --> C["集成测试 ~20%"]
    A --> D["E2E 测试 ~10%"]
    
    B --> B1["纯函数 / util"]
    B --> B2["自定义 Hook"]
    B --> B3["原子组件（Button）"]
    
    C --> C1["多组件交互流程"]
    C --> C2["表单提交 → API → 状态更新"]
    
    D --> D1["用户旅程：登录→搜索→下单"]
    
    style B fill:#4FC08D,color:#fff
    style C fill:#F5A87D,color:#000
    style D fill:#61DAFB,color:#000
```

## 环境配置

```jsonc
// vitest.config.ts
import { defineConfig } from "vitest/config";
import react from "@vitejs/plugin-react";

export default defineConfig({
  plugins: [react()],
  test: {
    environment: "jsdom",         // 模拟浏览器 DOM
    setupFiles: "./src/test/setup.ts",
    globals: true,
  },
});
```

```ts
// src/test/setup.ts
import "@testing-library/jest-dom/vitest";  // 扩展 expect 匹配器
import { vi } from "vitest";

// Mock window.matchMedia（解决媒体查询测试报错）
Object.defineProperty(window, "matchMedia", {
  writable: true,
  value: vi.fn().mockImplementation(query => ({
    matches: false,
    media: query,
    onchange: null,
    addListener: vi.fn(),   // deprecated
    removeListener: vi.fn(), // deprecated
    addEventListener: vi.fn(),
    removeEventListener: vi.fn(),
    dispatchEvent: vi.fn(),
  })),
});
```

## RTL 核心哲学

> [!tip] RTL 设计原则
> - **测试行为，不测试实现** — 关注用户能感知到的东西（文本、按钮、网络请求）
> - **像用户一样思考** — 用 `screen.getByRole("button", { name: "Submit" })` 而非 `.querySelector(".btn-primary"`
> - **断言明确期望的结果** — 不要测试 state 的值，测试渲染输出

```tsx
// ❌ 反例：耦合于内部实现
expect(component.state.count).toBe(2);
expect(wrapper.find(Button).length).toBe(1);

// ✅ 正例：基于用户感知
const button = screen.getByRole("button", { name: /add/i });
userEvent.click(button);
await screen.findByText(/added!/i);
```

## 组件单元测试

### 基础模式

```tsx
import { render, screen, fireEvent, waitFor } from "@testing-library/react";
import userEvent from "@testing-library/user-event";
import { Counter } from "./Counter";

describe("<Counter />", () => {
  it("初始显示 0", () => {
    render(<Counter initial={0} />);
    expect(screen.getByText("0")).toBeInTheDocument();
  });

  it("点击按钮后计数增加", async () => {
    render(<Counter initial={0} />);
    const button = screen.getByRole("button");
    
    await userEvent.click(button);
    expect(screen.getByText("1")).toBeInTheDocument();
    
    await userEvent.click(button);
    await userEvent.click(button);
    expect(screen.getByText("3")).toBeInTheDocument();
  });

  it("禁用态不可点击", () => {
    render(<Counter disabled initial={0} />);
    const button = screen.getByRole("button");
    expect(button).toBeDisabled();
  });
});
```

### Props 驱动 UI

```tsx
describe("<UserCard />", () => {
  it("显示用户基本信息", () => {
    render(<UserCard user={{ name: "Alice", role: "admin" }} />);
    expect(screen.getByText("Alice")).toBeInTheDocument();
    expect(screen.getByRole("img", { name: /avatar/i })).toHaveAttribute("alt", "Alice avatar");
  });

  it("显示操作菜单当 admin 时", () => {
    render(<UserCard user={{ name: "Alice", role: "admin" }} />);
    expect(screen.getByRole("button", { name: /edit/i })).toBeInTheDocument();
  });

  it("普通用户不显示操作菜单", () => {
    render(<UserCard user={{ name: "Bob", role: "user" }} />);
    expect(screen.queryByRole("button", { name: /edit/i })).not.toBeInTheDocument();
  });
});
```

## Mock 异步操作

```tsx
it("loading 态在请求完成后消失", async () => {
  vi.mocked(fetch).mockResolvedValueOnce({
    ok: true,
    json: async () => [{ id: 1, name: "Test" }],
  } as Response);
  
  render(<TodoList />);
  
  // 等待 loading 态出现再消失
  const spinner = await screen.findByRole("status");
  expect(spinner).toHaveTextContent("Loading...");
  
  // 数据渲染完成
  const item = await screen.findByText("Test");
  expect(item).toBeInTheDocument();
});

it("网络错误显示错误提示", async () => {
  vi.mocked(fetch).mockRejectedValueOnce(new Error("Network error"));
  
  render(<TodoList />);
  
  await waitFor(() => {
    expect(screen.getByText("Failed to load")).toBeInTheDocument();
  });
});
```

## Hook 测试

```tsx
import { renderHook, act } from "@testing-library/react";
import { useDebounce } from "../hooks/useDebounce";

describe("useDebounce", () => {
  beforeEach(() => vi.useFakeTimers());
  afterEach(() => vi.useRealTimers());

  it("值不变时返回原始值", () => {
    const { result } = renderHook(({ value }) => useDebounce(value, 300), {
      initialProps: { value: "hello", delay: 300 },
    });
    
    expect(result.current).toBe("hello");
  });

  it("延迟后返回新值", async () => {
    const { result, rerender } = renderHook(
      ({ value }) => useDebounce(value, 300),
      { initialProps: { value: "a" } }
    );
    
    rerender({ value: "b" });
    expect(result.current).toBe("a");  // 尚未变化
    
    act(() => vi.advanceTimersByTime(300));
    expect(result.current).toBe("b");  // 防抖完成
  });
});
```

## E2E 测试选择

| 工具 | 适用场景 | 特点 |
|------|----------|------|
| **Playwright** | 全功能 E2E（推荐） | 跨浏览器、内置 trace、重试机制 |
| **Cypress** | 可视化调试友好 | DevTools 体验好、社区活跃 |
| **Puppeteer** | Google 官方、精细控制 | 底层 API、灵活性高 |

> [!note] E2E 边界
> - E2E 只应覆盖**关键用户旅程**（登录、下单、支付）
> - 不要为每个页面的每个字段写 E2E——那属于集成测试的范畴

## 关联笔记