5.5.3 breaks testing for React 15

[alexzherdev]

• react-testing-library version: 5.5.3
• react version: 15.6.2
• node version: 10
• npm (or yarn) version: yarn 1.13

Relevant code or config:

import React from "react";
import { render } from "react-testing-library";
render(<div />);

What you did:

Just recently installed the library and was trying to write my first tests. Everything was working fine until I updated to 5.5.3.

What happened:

Trying to render anything in tests results in ReactDOM.render(): Invalid component element.

Reproduction:

https://codesandbox.io/s/lxzrym3p9q

Problem description:

This seems to be the culprit: https://github.com/kentcdodds/react-testing-library/blob/1d45c5c2ca1281187dc7735ac0e2f12137b157d3/src/act-compat.js#L10
Rendering null only works in React 16, not in 15.x.

Suggested solution:

I'm actually not too sure why that line is necessary in the first place. Why is just calling ReactDOM.unstable_batchedUpdates not enough?

[kentcdodds]

Ah, yep, that'll do it. The fix is to render <div /> instead of null. Want to make a pull request for that?

[kentcdodds]

🎉 This issue has been resolved in version 5.5.4 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀