POST Request Hangs on multipart/form-data Response

[blackjacques]

Describe the bug

Node.js version: 22.11.0

OS version: Windows 10 Home

Description: I am testing an Express API that returns a multipart/form-data response using the form-data library. When invoking the post() method, it hangs until the test times out.

Actual behavior

The post method never resolves and the test times out.
The exact error is:

Jest has detected the following 1 open handle potentially keeping Jest from exiting:

● TCPSERVERWRAP

  195 |       });
  196 |       */
> 197 |       const result = await api.post('/')
      |                                ^
  198 |             .send()
  199 |             .set('Content-Type', 'multipart/form-data')
  200 |             .set('Accept', 'multipart/form-data');

  at Test.serverAddress (node_modules/supertest/lib/test.js:48:35)
  at new Test (node_modules/supertest/lib/test.js:34:14)
  at Object.obj.<computed> [as post] (node_modules/supertest/index.js:43:18)
  at Object.post (__tests__/test.js:197:32)

Expected behavior

It should return a multipart/form-data response that I can inspect.

Code to reproduce

// server code:
const app = express();
const FormData = require('form-data');

app.post("/", async (req, res) => {
  const form = new FormData();
  form.append('errors', 'there was an error');
  res.writeHead(200, {
    'Content-Type': `multipart/form-data; boundary=${form.getBoundary()}`, // boundary must match the one generated by form-data
    'Content-Length': form.getLengthSync(),
    'Access-Control-Allow-Credentials': 'true',
    'Access-Control-Allow-Origin': '*', // Update based on your needs (for demo purposes, '*' is more flexible)
  });

  // Write the multipart form data response.
  res.write(form.getBuffer());
  res.end();
});

// in test.js:
it('should return errors about missing params', async () => {
  const result = await api.post('/')
            .send()
            .set('Content-Type', 'multipart/form-data')
            .set('Accept', 'multipart/form-data');
  expect(result).not.toBeNull();
  expect(result.body).not.toBeNull();
});

Checklist

• I have searched through GitHub issues for similar issues.
• I have completely read through the README and documentation.
• I have tested my code with the latest version of Node.js and this package and confirmed it is still not working.