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Add testAsync example with ReactTestUtils actAsync usage #77

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Add testAsync example with ReactTestUtils actAsync usage #77

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34 changes: 34 additions & 0 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -44,6 +44,40 @@ describe("Expect.Operators", () => {

```

`testAsync` example with ReactTestUtils `actAsync` for effectfull component assertion:

```reason
open Jest;

describe("ReactTestUtils actAsync", () => {
open Expect;
open Js.Promise;
open ReactTestUtils;

let container = ref(None);
beforeEach(prepareContainer(container));
afterEach(cleanupContainer(container));

let effectfulComponent = <p>{"Hello async Jest" |> React.string}</p>

// use testAsync to get a `finish` callback for final assertion
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;
});
Comment on lines +64 to +77
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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.

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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 ) ?

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

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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?

});
```

See [the tests](https://github.com/glennsl/bs-jest/tree/master/__tests__) for more examples.

## Installation
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