Add testAsync example with ReactTestUtils actAsync usage

[TristanCacqueray]

No description provided.

[TristanCacqueray]

Not sure this README is the appropriate place for such example, but as it took me quite a while to figure out this usage, and assuming this is the right strategy, perhaps bs-jest could document how it can be used to test react hook?

[glennsl]

Thanks! I don't know where else to put this, so I think this is fine. It would probably be better to use testPromise though, as shown below, if you could verify that this works?

[glennsl]

It would be more appropriate to use testPromise here, I think. Then you should be able to do:

Suggested change

	testAsync("actAsync", finish => {
	let container = getContainer(container);
	// actAsync returns a promise for all effects evaluation
	actAsync(_ =>
	// Convert ReactDOMRe.render to a promise
	resolve(ReactDOMRe.render(effectfulComponent, container))
	) |> then_(_ =>
	// Call finish with assertion on final container
	finish(expect(
	container
	->DOM.findBySelectorAndTextContent("p", "Hello async Jest")
	->Belt.Option.isSome) |> toBe(true)) |> resolve
	) |> ignore;
	});
	testPromise("actAsync", () => {
	let container = getContainer(container);
	// actAsync returns a promise for all effects evaluation
	actAsync(_ =>
	// Convert ReactDOMRe.render to a promise
	resolve(ReactDOMRe.render(effectfulComponent, container))
	) |> then_(_ =>
	// Call finish with assertion on final container
	expect(
	container
	->DOM.findBySelectorAndTextContent("p", "Hello async Jest")
	->Belt.Option.isSome) |> toBe(true) |> resolve
	);
	});

Slightly simpler and much safer.

[TristanCacqueray]

That looks much better, unfortunately that does not seems to work with actAsync, here is the error message:

    TypeError: Cannot read property 'then' of undefined

      at Object.<anonymous> (node_modules/@glennsl/bs-jest/src/jest.bs.js:249:47)

Could it be caused by the actAsync binding implementation ( https://github.com/reasonml/reason-react/blob/5ae20e8a6245a584a8f452bf797a2ac26c09d873/src/ReactTestUtils.re#L22-L28 ) ?

[TristanCacqueray]

For some reason, it seems like actAsync resulting promise can only be resolved once. e.g. actAsync(_ => () |> resolve) |> then_(_ => () |> resolve) is undefined.

[glennsl]

Huh, that's weird. They do seem to return a broken thenable. I can't imagine why they would do that without documenting it. Definitely seems like a bug, so perhaps it would be a good idea to open an issue on the react repo?