Using delay('infinite') leaves unresolved promises which make jest warn

Describe the bug

⚠️ I’m not sure if this is the correct repo to report this.

When trying to use delay('infinite') to mock loading states, jest throws a warning and hangs forever.

Jest did not exit one second after the test run has completed.

This usually means that there are asynchronous operations that weren't stopped
in your tests. Consider running Jest with `--detectOpenHandles` to troubleshoot
this issue.

This happens because the promises hang forever, but I can’t find a way to cancel/reject/terminate them. I’m not really sure what’s the correct way of handling this.

Environment

• msw: 0.29.0
• nodejs: 14.17.0
• npm: 7.15.1

To Reproduce

// sample.spec.js

const { rest } = require('msw');
const { setupServer } = require('msw/node');

const fetch = require('node-fetch');

it('hangs', () => {
  const server = setupServer();

  server.listen();

  server.use(rest.get('http://localhost/a-request', (_req, res, ctx) => res(ctx.delay('infinite'))));

  fetch('http://localhost/a-request').then(() => undefined).catch(console.error);

  expect(true).toBe(true);

  server.close();
});

Just to give some extra context, the real code is more like:

it('shows a loading spinner', async () => {
	render(<Component />);

	const loadingBar = await findByRole('progressbar')

	expect(loadingBar).toBeInTheDocument();
});

Expected behavior

Requests are aborted(?), the tests conclude and jest doesn’t warn about opened handlers.

Screenshots

[DannyBiezen]

I just ran into this issue as well. It’d be great to have support for this as currently quite a lot of my tests have to use an arbitrary delay which makes them flaky.

[kettanaito]

I think with the new interceptors architecture we should be able to hard-cancel all pending promises on process.on('exit') and friends. It’s a matter of force-resolving/rejecting this Promise queue. At least, this is a good place to start, as all interceptors facilitate AsyncEventEmitter to await potential listeners.

Contributions are welcome!