[test] Enable "missing act()"-warnings

[eps1lon]

Enables missing act warnings to enforce wrapping updates in act.

This will later be required for concurrent react and brings the test closer to how a jest-user would test.

I was wondering for the longest time why we didn't need act() all the time and it turns out these warnings are simply disabled outside of jest.

There are some cases why we shouldn't need act in my opinion (e.g. facebook/react#19318) which we can later revisit.

[mui-pr-bot]

Details of bundle changes

Generated by 🚫 dangerJS against 6b12c72

[oliviertassinari]

I thought testing library already included act when firing events

Suggested change

	act(() => {
	input.focus();
	fireEvent.change(document.activeElement, { target: { value: 'a' } });
	});
	act(() => {
	input.focus();
	});
	fireEvent.change(document.activeElement, { target: { value: 'a' } });

[eps1lon]

Yeah it does. That doesn't necessarily mean that we can't put these in a single act() because that's a difference in behavior:

act(one);
// two runs with updates flushed from one
act(two)

vs

act(() => {
  one();
  // two runs without all updates flushed from one (I think)
  two();
})

I'm not 100% certain these are different. Though I would expect that idle or offscreen updates scheduled in one are not necessarily flushed before two runs.

I'll try to wrap actions for an assertion in a single act() i.e. between each act() should be an assertion.

In the end wrapping it in a single act() is closer to the original behavior which is more important here.

[oliviertassinari]

Interesting distinction, I will keep it in mind.

So, we should consider if two actions will happen during the same screen frame, in between 16ms, or not. If it's two consequent events, like mouseup/click, it should be wrapped in the same act, if it's two user actions, like key down + key up, it should be wrapped in two acts.

Correct?

[eps1lon]

I'm not sure to be honest. It seems to me that as few acts as possible should be preferred because the "time" between two acts() can be very long

[oliviertassinari]

Ok, time will tell 🤷‍♂️