Enzyme: wrapper.simulate() should be wrapped in ReactTestUtils.act()

[mikesteele]

Is your feature request related to a problem? Please describe.
React 16.8 introduced act() to allow component interactions to be tested in a synchronous way.

Describe the solution you'd like
wrapper.simulate() should be wrapped in act() to ensure any state changes are resolved before proceeding.

Describe alternatives you've considered

act(() => {
  wrapper.simulate();
});

Though it's easy to forget act.

Additional context
I have a feeling this is already on your roadmap, but I couldn't find an issue about it.

[ljharb]

This is already addressed by #2034.

[mikesteele]

Out of curiosity, does that PR mean that any time a mounted component is rendered, it's wrapped in act()? Or only on mount()?

[ljharb]

Only mount mounts components, so yes to both?

Shallow rendering does not yet have an “act”, so that’s still unaddressed.

[jquense]

@ljharb sorry how does #2034 address this? It seems like that only wraps mount() calls in act()? simulate() should _also_ wrap calls, which is not what's happening on the latest published enzyme

[ljharb]

@jquense there's a bunch of unpublished stuff in enzyme, for one, but you're right that simulate probably isn't covered. A PR to fix that would be great.

act requires a DOM, and there's no act that works in a non-browser environment, so it's simply not an option for shallow at this time.

[mikesteele]

Could you re-open this issue then?

[ljharb]

It’s not fixable by enzyme until the shallow renderer provides an act, but sure.

[mikesteele]

But it's not fixable for simulate in full DOM rendering?

[ljharb]

Ah, true, that is fixable. PRs welcome :-) even if they only have test cases.

[mikesteele]

Thanks! I'll try to find time to contribute. I think this will be a huge improvement for users who need to force wrappers to update after simulating events to ensure that state updates are complete.

[jquense]

@mikesteele let me know if you don't have any time . i'd be happy to put something together as well

[ljharb]

Feel free to race each other to get something up :-p thanks in advance! <3

[mikesteele]

@jquense I probably won't have time for a few weeks, feel free to take this