Sebastian MarkbågeandGitHub
fe91bdbcbe
Stacked on #31975. This is the primary way we recommend styling your View Transitions since it allows for reusable styling such as a CSS library specializing in View Transitions in a way that's composable and without naming conflicts. E.g. ```js <ViewTransition className="enter-slide-in exit-fade-out update-cross-fade"> ``` This doesn't change the HTML `class` attribute. It's not a CSS class. Instead it assign the `view-transition-class` style prop of the underlying DOM node while it's transitioning. You can also just use `<div style={{viewTransitionClass: ...}}>` on the DOM node but it's convenient to control the Transition completely from the outside and conceptually we're transitioning the whole fragment. You can even make Transition components that just wraps existing components. `<RevealTransition><Component /></RevealTransition>` this way. Since you can also have multiple wrappers for different circumstances it allows React's heuristics to use different classes for different scenarios. We'll likely add more options like configuring different classes for different `types` or scenarios that can't be described by CSS alone. ## CSS Modules ```js import transitions from './transitions.module.css'; <ViewTransition className={transitions.bounceIn}>...</ViewTransition> ``` CSS Modules works well with this strategy because you can have globally unique namespaces and define your transitions in the CSS modules as a library that you can import. [As seen in the fixture here.](https://github.com/facebook/react/commit/8b91b37bb8b4add5f3f8be5ef8f49bb23966b13b#diff-b4d9854171ffdac4d2c01be92a5eff4f8e9e761e6af953094f99ca243b054a85R11) I did notice an unfortunate bug in how CSS Modules (at least in Webpack) generates class names. Sometimes the `+` character is used in the hash of the class name which is not valid for `view-transition-class` and so it breaks. I had to rename my class names until the hash yielded something different to work around it. Ideally that bug gets fixed soon. ## className, rly? `className` isn't exactly the most loved property name, however, I'm using `className` here too for consistency. Even though in this case there's no direct equivalent DOM property name. The CSS property is named `viewTransitionClass`, but the "viewTransition" prefix is implied by the Component it is on in this case. For most people the fact that this is actually a different namespace than other CSS classes doesn't matter. You'll most just use a CSS library anyway and conceptually you're just assigning classes the same way as `className` on a DOM node. But if we ever rename the `class` prop then we can do that for this one as well.
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.