`FALLBACK_THROTTLE_MS` slows tests down significantly - could it be configurable? about react HOT 4 OPEN

For context, this throttling could be experienced in React 18 with a larger value (500ms). React 19 used it in more scenarios which lead to the decision to reduce the value.

from react.

That's very possible, but tbh. we haven't encountered a single situation in our tests where it triggered with React 18 (at least none of our suspense-related test takes over 500ms) - of course that might have been due to the very specific nature of our tests.
Otherwise, you would probably have gotten this request sooner 😉

from react.

There's no need to make it configurable since the throttle heuristic is already skipped when resolved during act.

You can fix this today by manually resolving e.g.

let resolve: (value: string) => void;
const initialPromise = new Promise<string>((_resolve) => {
  resolve = _resolve;
});
...
await act(async () => {
  resolve("test");
});

We'll likely deprecate non-awaited act at some point so that you can just write

-await act(async () => {
+await act(() => {

Though at that point you wouldn't need to manually resolve anyway since await render would've flushed the revealed content. Work for that is being tracked in testing-library/react-testing-library#1214. Note that await render(...) is not sufficient today.

from react.

This kinda goes opposite to the "you probably don't want to use act at all" advice over in #30031 (comment) 😞

We cannot really have both if this is the only way of avoiding that heuristic. But since the heuristic apparently already is in place, would it be possible to introduce a different way to opt out on top?

from react.