如何消除Jest+MSW v2中FormData请求单元测试的泄漏警告？

在Node18环境的React项目中，将Jest+MSW v1的单元测试迁移到MSW v2后，当请求体为FormData类型时，控制台出现以下警告：

A worker process has failed to exit gracefully and has been force exited. This is likely caused by tests leaking due to improper teardown. Try running with --detectOpenHandles to find leaks. Active timers can also cause this, ensure that .unref() was called on them.

仅在请求体为FormData（无论内容是文件还是字符串）时触发该警告，字符串或对象类型的请求体无此问题。相关测试代码如下：

测试代码1（文件作为FormData） #

it('requests endpoint with a file as formdata', async () => {
  server.use(
    http.post('/endpoint', async ({ request }) => {
      requests.push(request);
      return HttpResponse.json({ data: 'some data' });
    }),
  );

  const file = new File(
    [fs.readFileSync(path.join(__dirname, '__fixtures__', 'file.png'))],
    'file.png',
  );

  const body = new FormData();
  body.append('file', file);

  // internal functionality
  await expect(postToBackend({
    endpoint: '/endpoint',
    body,
  })).resolves.toEqual({ data: 'some data' });

  body.delete('file');
  expect(requests).toHaveLength(1);
});

测试代码2（字符串作为FormData） #

it('requests endpoint with a string as formdata', async () => {
  server.use(
    http.post('/endpoint', async ({ request }) => {
      requests.push(request);
      return HttpResponse.json({ data: 'some data' });
    }),
  );

  const body = new FormData();
  body.append('file', 'some form data');

  // internal functionality
  await expect(postToBackend({
    endpoint: '/endpoint',
    body,
  })).resolves.toEqual({ data: 'some data' });

  body.delete('file');
  expect(requests).toHaveLength(1);
});

以下几种方法可消除该警告：

1. 在Mock Handler中消费FormData请求体 #

MSW v2中Request对象的body是可读流，若未被消费会导致资源泄漏。在mock接口中主动读取并消费FormData：

http.post('/endpoint', async ({ request }) => {
  // 消费FormData，释放关联资源
  await request.formData();
  requests.push(request);
  return HttpResponse.json({ data: 'some data' });
}),

2. 测试后手动销毁Request对象 #

在断言完成后，主动销毁保存的Request对象，释放资源：

await expect(postToBackend({
  endpoint: '/endpoint',
  body,
})).resolves.toEqual({ data: 'some data' });

// 取消请求流并清空数组，释放引用
await requests[0].body.cancel();
requests = [];

body.delete('file');
expect(requests).toHaveLength(1);

3. 完善MSW服务器的清理逻辑 #

在每个测试用例结束后，重置MSW处理器并清空请求数组，避免残留引用：

afterEach(() => {
  server.resetHandlers();
  requests = []; // 清空请求数组，释放Request对象的内存引用
});

4. 临时应急：配置Jest强制退出（不推荐长期使用） #

在package.json的测试脚本中添加--forceExit参数，强制Jest在测试结束后退出进程：

"scripts": {
  "test": "jest --forceExit"
}

内容的提问来源于stack exchange，提问作者axel