https://codesandbox.io/s/upbeat-frost-3tt25

1. Press Suspend, see "Loading..."
2. Wait five seconds, you'll see "Happy birthday" at some point 
3. You won't see it again no matter how long you wait

Expected: you'll see it every five seconds.
React.unstable_withSuspenseConfig(
      () => {
        ReactNoop.render(<App showContent={true} />);
      },
      {timeoutMs: 5000},
    );
    expect(Scheduler).toFlushAndYield(['Suspend! [A]', 'Loading...']);
    Scheduler.unstable_advanceTime(2000);
    await advanceTimers(2000);
    expect(Scheduler).toHaveYielded(['Promise resolved [A]']);
    expect(Scheduler).toFlushAndYieldThrough(['A', 'Commit']);
    expect(ReactNoop).toMatchRenderedOutput(
      <>
        <div hidden={true} />
        <span prop="A" />
      </>,
    );
    expect(Scheduler).toFlushAndYield(['A', 'Offscreen']);
    expect(ReactNoop).toMatchRenderedOutput(
      <>
        <div hidden={true}>
          <span prop="A" />
          Offscreen
        </div>
        <span prop="A" />
      </>,
    );
  });
});