Triggering a revalidation from tests

[joshkel]

How do I trigger a revalidation when using React Testing Library? I'd like to test my SWR error handling and how my code handles transitioning from valid to error state. Sample code, using Jest, Testing Library, and MSW:

/** @jest-environment jsdom */
import { render, screen } from '@testing-library/react';
import { rest } from 'msw';
import { setupServer } from 'msw/node';
import React from 'react';
import useSWR from 'swr';

const fetcher = (...args: Parameters<typeof fetch>) =>
  fetch(...args).then(async (res) => {
    if (!res.ok) {
      throw new Error(await res.text());
    } else {
      return res.json();
    }
  });

describe('SWR error handling', () => {
  let success = true;

  const server = setupServer(
    rest.get('/test', (req, res, ctx) => {
      console.log('Requested with ' + success);
      return success ? res(ctx.json('Hello, world!')) : res(ctx.json('Oh no!'), ctx.status(404));
    })
  );
  beforeAll(() => server.listen());
  afterAll(() => server.close());

  function TestComponent() {
    const { data, error } = useSWR('/test', { fetcher, revalidateOnMount: true });
    console.log({ data, error });
    return (
      <>
        {data && 'Loaded: ' + data}
        {error && 'Error: ' + error}
      </>
    );
  }

  it('displays a message on error', async () => {
    const { rerender } = render(<TestComponent key={1} />);
    expect(await screen.findByText(/Loaded/)).toBeInTheDocument();

    success = false;
    rerender(<TestComponent key={2} />);
    expect(await screen.findByText(/Error/)).toBeInTheDocument();
  });
});

I'm passing key to mount a new component. The console log messages show that the first component mounts and renders and the MSW handler is invoked (as expected), and then the second component mounts and renders with the stale data (as expected), but the MSW handler is never re-invoked.

I'm assuming that there's something to do with the various promises and effects used by SWR, but I'm not sure how to properly process and flush them.

Any ideas?