Provide a way to trigger useEffect from tests

Hello,

I tried testing components that use the cool new hooks API, but useEffect doesn’t seem to work with the test renderer.

Here’s a small failling Jest test:

import React, { useEffect } from "react";
import { create as render } from "react-test-renderer";

it("calls effect", () => {
  return new Promise(resolve => {
    render(<EffectfulComponent effect={resolve} />);
  });
});

function EffectfulComponent({ effect }) {
  useEffect(effect);

  return null;
}

And here’s a minimal reproducing repo: https://github.com/skidding/react-test-useeffect

Note that other use APIs seemed to work (eg. useContext).

[gaearon]

We should have something to trigger them.

[danielkcz]

I think you don’t need such a hassle for this. Jest would automock if you create a file <root>/__mocks__/react.js and in there you can just…

const React = require.actual('react')
module.exports = { ...React, useEffect: React.useLayoutEffect }

This is a great workaround as you don’t need to touch any code when this is somehow fixed, you will just remove the mock.