4c12339ce3
This PR moves `flushSync` out of the reconciler. there is still an internal implementation that is used when these semantics are needed for React methods such as `unmount` on roots. This new isomorphic `flushSync` is only used in builds that no longer support legacy mode. Additionally all the internal uses of flushSync in the reconciler have been replaced with more direct methods. There is a new `updateContainerSync` method which updates a container but forces it to the Sync lane and flushes passive effects if necessary. This combined with flushSyncWork can be used to replace flushSync for all instances of internal usage. We still maintain the original flushSync implementation as `flushSyncFromReconciler` because it will be used as the flushSync implementation for FB builds. This is because it has special legacy mode handling that the new isomorphic implementation does not need to consider. It will be removed from production OSS builds by closure though
react-test-renderer (DEPRECATED)
Deprecation notice
react-test-renderer is deprecated and no longer maintained. It will be removed in a future version. As of React 19, you will see a console warning when invoking ReactTestRenderer.create().
React Testing
This library creates a contrived environment and its APIs encourage introspection on React's internals, which may change without notice causing broken tests. It is instead recommended to use browser-based environments such as jsdom and standard DOM APIs for your assertions.
The React team recommends @testing-library/react as a modern alternative that uses standard APIs, avoids internals, and promotes best practices.
React Native Testing
The React team recommends @testing-library/react-native as a replacement for react-test-renderer for native integration tests. This React Native testing-library variant follows the same API design as described above and promotes better testing patterns.
Documentation
This package provides an experimental React renderer that can be used to render React components to pure JavaScript objects, without depending on the DOM or a native mobile environment.
Essentially, this package makes it easy to grab a snapshot of the "DOM tree" rendered by a React DOM or React Native component without using a browser or jsdom.
Documentation: https://reactjs.org/docs/test-renderer.html
Usage:
const ReactTestRenderer = require('react-test-renderer');
const renderer = ReactTestRenderer.create(
<Link page="https://www.facebook.com/">Facebook</Link>
);
console.log(renderer.toJSON());
// { type: 'a',
// props: { href: 'https://www.facebook.com/' },
// children: [ 'Facebook' ] }
You can also use Jest's snapshot testing feature to automatically save a copy of the JSON tree to a file and check in your tests that it hasn't changed: https://jestjs.io/blog/2016/07/27/jest-14.html.