chore: update React examples to match with the new React guidelines

CHANGELOG.md

@@ -22,6 +22,7 @@
 - `[*]` [**BREAKING**] Drop support for Node v10 and v15 and target first LTS `16.13.0` ([#12220](https://github.com/facebook/jest/pull/12220))
 - `[*]` [**BREAKING**] Drop support for `[email protected]`, minimum version is now `4.2` ([#11142](https://github.com/facebook/jest/pull/11142))
 - `[*]` Bundle all `.d.ts` files into a single `index.d.ts` per module ([#12345](https://github.com/facebook/jest/pull/12345))
+- `[docs, examples]` Update React examples to match with the new React guidelines for code examples ([#12217](https://github.com/facebook/jest/pull/12217))
 - `[expect]` [**BREAKING**] Remove support for importing `build/utils` ([#12323](https://github.com/facebook/jest/pull/12323))
 - `[expect]` [**BREAKING**] Migrate to ESM ([#12344](https://github.com/facebook/jest/pull/12344))
 - `[jest-cli]` Update `yargs` to v17 ([#12357](https://github.com/facebook/jest/pull/12357))

docs/SnapshotTesting.md

@@ -12,7 +12,6 @@ A typical snapshot test case renders a UI component, takes a snapshot, then comp
 A similar approach can be taken when it comes to testing your React components. Instead of rendering the graphical UI, which would require building the entire app, you can use a test renderer to quickly generate a serializable value for your React tree. Consider this [example test](https://github.com/facebook/jest/blob/main/examples/snapshot/__tests__/link.test.js) for a [Link component](https://github.com/facebook/jest/blob/main/examples/snapshot/Link.js):
 
 ```tsx
-import React from 'react';
 import renderer from 'react-test-renderer';
 import Link from '../Link';
 

docs/TutorialReact.md

@@ -48,7 +48,10 @@ Your `package.json` should look something like this (where `<current-version>` i
 
 ```js title="babel.config.js"
 module.exports = {
-  presets: ['@babel/preset-env', '@babel/preset-react'],
+  presets: [
+    '@babel/preset-env',
+    ['@babel/preset-react', {runtime: 'automatic'}],
+  ],
 };
 ```
 
@@ -59,14 +62,14 @@ module.exports = {
 Let's create a [snapshot test](SnapshotTesting.md) for a Link component that renders hyperlinks:
 
 ```tsx title="Link.js"
-import React, {useState} from 'react';
+import {useState} from 'react';
 
 const STATUS = {
   HOVERED: 'hovered',
   NORMAL: 'normal',
 };
 
-const Link = ({page, children}) => {
+export default function Link({page, children}) {
   const [status, setStatus] = useState(STATUS.NORMAL);
 
   const onMouseEnter = () => {
@@ -87,35 +90,36 @@ const Link = ({page, children}) => {
       {children}
     </a>
   );
-};
-
-export default Link;
+}
 ```
 
 > Note: Examples are using Function components, but Class components can be tested in the same way. See [React: Function and Class Components](https://reactjs.org/docs/components-and-props.html#function-and-class-components). **Reminders** that with Class components, we expect Jest to be used to test props and not methods directly.
 
 Now let's use React's test renderer and Jest's snapshot feature to interact with the component and capture the rendered output and create a snapshot file:
 
 ```tsx title="Link.react.test.js"
-import React from 'react';
-import renderer from 'react-test-renderer';
 import Link from '../Link.react';
+import renderer from 'react-test-renderer';
 
-test('Link changes the class when hovered', () => {
+it('changes the class when hovered', () => {
   const component = renderer.create(
     <Link page="http://www.facebook.com">Facebook</Link>,
   );
   let tree = component.toJSON();
   expect(tree).toMatchSnapshot();
 
   // manually trigger the callback
-  tree.props.onMouseEnter();
+  renderer.act(() => {
+    tree.props.onMouseEnter();
+  });
   // re-rendering
   tree = component.toJSON();
   expect(tree).toMatchSnapshot();
 
   // manually trigger the callback
-  tree.props.onMouseLeave();
+  renderer.act(() => {
+    tree.props.onMouseLeave();
+  });
   // re-rendering
   tree = component.toJSON();
   expect(tree).toMatchSnapshot();
@@ -125,32 +129,35 @@ test('Link changes the class when hovered', () => {
 When you run `yarn test` or `jest`, this will produce an output file like this:
 
 ```javascript title="__tests__/__snapshots__/Link.react.test.js.snap"
-exports[`Link changes the class when hovered 1`] = `
+exports[`changes the class when hovered 1`] = `
 <a
   className="normal"
   href="http://www.facebook.com"
   onMouseEnter={[Function]}
-  onMouseLeave={[Function]}>
+  onMouseLeave={[Function]}
+>
   Facebook
 </a>
 `;
 
-exports[`Link changes the class when hovered 2`] = `
+exports[`changes the class when hovered 2`] = `
 <a
   className="hovered"
   href="http://www.facebook.com"
   onMouseEnter={[Function]}
-  onMouseLeave={[Function]}>
+  onMouseLeave={[Function]}
+>
   Facebook
 </a>
 `;
 
-exports[`Link changes the class when hovered 3`] = `
+exports[`changes the class when hovered 3`] = `
 <a
   className="normal"
   href="http://www.facebook.com"
   onMouseEnter={[Function]}
-  onMouseLeave={[Function]}>
+  onMouseLeave={[Function]}
+>
   Facebook
 </a>
 `;
@@ -160,7 +167,7 @@ The next time you run the tests, the rendered output will be compared to the pre
 
 The code for this example is available at [examples/snapshot](https://github.com/facebook/jest/tree/main/examples/snapshot).
 
-#### Snapshot Testing with Mocks, Enzyme and React 16
+#### Snapshot Testing with Mocks, Enzyme and React 16+
 
 There's a caveat around snapshot testing when using Enzyme and React 16+. If you mock out a module using the following style:
 
@@ -205,9 +212,9 @@ You have to run `yarn add --dev @testing-library/react` to use react-testing-lib
 Let's implement a checkbox which swaps between two labels:
 
 ```tsx title="CheckboxWithLabel.js"
-import React, {useState} from 'react';
+import {useState} from 'react';
 
-const CheckboxWithLabel = ({labelOn, labelOff}) => {
+export default function CheckboxWithLabel({labelOn, labelOff}) {
   const [isChecked, setIsChecked] = useState(false);
 
   const onChange = () => {
@@ -220,13 +227,10 @@ const CheckboxWithLabel = ({labelOn, labelOff}) => {
       {isChecked ? labelOn : labelOff}
     </label>
   );
-};
-
-export default CheckboxWithLabel;
+}
 ```
 
 ```tsx title="__tests__/CheckboxWithLabel-test.js"
-import React from 'react';
 import {cleanup, fireEvent, render} from '@testing-library/react';
 import CheckboxWithLabel from '../CheckboxWithLabel';
 
@@ -256,11 +260,14 @@ You have to run `yarn add --dev enzyme` to use Enzyme. If you are using a React
 Let's rewrite the test from above using Enzyme instead of react-testing-library. We use Enzyme's [shallow renderer](http://airbnb.io/enzyme/docs/api/shallow.html) in this example.
 
 ```tsx title="__tests__/CheckboxWithLabel-test.js"
-import React from 'react';
-import {shallow} from 'enzyme';
+import Enzyme, {shallow} from 'enzyme';
+import Adapter from 'enzyme-adapter-react-16';
+
+Enzyme.configure({adapter: new Adapter()});
+
 import CheckboxWithLabel from '../CheckboxWithLabel';
 
-test('CheckboxWithLabel changes the text after click', () => {
+it('CheckboxWithLabel changes the text after click', () => {
   // Render a checkbox with label in the document
   const checkbox = shallow(<CheckboxWithLabel labelOn="On" labelOff="Off" />);
 

examples/enzyme/.babelrc.js

@@ -1,6 +1,8 @@
 // Copyright (c) 2014-present, Facebook, Inc. All rights reserved.
 
 module.exports = {
-  presets: ['@babel/preset-env', '@babel/preset-react'],
-  plugins: ['@babel/plugin-proposal-class-properties']
+  presets: [
+    '@babel/preset-env',
+    ['@babel/preset-react', {runtime: 'automatic'}],
+  ],
 };

examples/enzyme/CheckboxWithLabel.js

@@ -1,26 +1,28 @@
 // Copyright 2004-present Facebook. All Rights Reserved.
 
-import React from 'react';
+import {useState} from 'react';
 
-export default class CheckboxWithLabel extends React.Component {
-  state = {
-    isChecked: false,
-  };
+export default function CheckboxWithLabel({
+  labelRef,
+  inputRef,
+  labelOn,
+  labelOff,
+}) {
+  const [isChecked, setIsChecked] = useState(false);
 
-  onChange = () => {
-    this.setState({isChecked: !this.state.isChecked});
+  const onChange = () => {
+    setIsChecked(!isChecked);
   };
 
-  render() {
-    return (
-      <label>
-        <input
-          type="checkbox"
-          checked={this.state.isChecked}
-          onChange={this.onChange}
-        />
-        {this.state.isChecked ? this.props.labelOn : this.props.labelOff}
-      </label>
-    );
-  }
+  return (
+    <label ref={labelRef}>
+      <input
+        ref={inputRef}
+        type="checkbox"
+        checked={isChecked}
+        onChange={onChange}
+      />
+      {isChecked ? labelOn : labelOff}
+    </label>
+  );
 }

examples/enzyme/__tests__/CheckboxWithLabel-test.js

@@ -1,6 +1,5 @@
 // Copyright 2004-present Facebook. All Rights Reserved.
 
-import React from 'react';
 import Enzyme, {shallow} from 'enzyme';
 import Adapter from 'enzyme-adapter-react-16';
 

examples/react-testing-library/.babelrc.js

@@ -1,6 +1,8 @@
 // Copyright (c) 2014-present, Facebook, Inc. All rights reserved.
 
 module.exports = {
-  presets: ['@babel/preset-env', '@babel/preset-react'],
-  plugins: ['@babel/plugin-proposal-class-properties'],
+  presets: [
+    '@babel/preset-env',
+    ['@babel/preset-react', {runtime: 'automatic'}],
+  ],
 };

examples/react-testing-library/CheckboxWithLabel.js

@@ -1,8 +1,8 @@
 // Copyright 2004-present Facebook. All Rights Reserved.
 
-import React, {useState} from 'react';
+import {useState} from 'react';
 
-const CheckboxWithLabel = ({labelOn, labelOff}) => {
+export default function CheckboxWithLabel({labelOn, labelOff}) {
   const [isChecked, setIsChecked] = useState(false);
 
   const onChange = () => {
@@ -15,6 +15,4 @@ const CheckboxWithLabel = ({labelOn, labelOff}) => {
       {isChecked ? labelOn : labelOff}
     </label>
   );
-};
-
-export default CheckboxWithLabel;
+}

examples/react-testing-library/__tests__/CheckboxWithLabel-test.js

@@ -1,6 +1,5 @@
 // Copyright 2004-present Facebook. All Rights Reserved.
 
-import React from 'react';
 import {cleanup, fireEvent, render} from '@testing-library/react';
 import CheckboxWithLabel from '../CheckboxWithLabel';
 

examples/react/.babelrc.js

@@ -1,5 +1,8 @@
 // Copyright (c) 2014-present, Facebook, Inc. All rights reserved.
 
 module.exports = {
-  presets: ['@babel/preset-env', '@babel/preset-react'],
+  presets: [
+    '@babel/preset-env',
+    ['@babel/preset-react', {runtime: 'automatic'}],
+  ],
 };

examples/react/CheckboxWithLabel.js

@@ -1,8 +1,13 @@
 // Copyright 2004-present Facebook. All Rights Reserved.
 
-import React, {useState} from 'react';
+import {useState} from 'react';
 
-const CheckboxWithLabel = ({labelRef, inputRef, labelOn, labelOff}) => {
+export default function CheckboxWithLabel({
+  labelRef,
+  inputRef,
+  labelOn,
+  labelOff,
+}) {
   const [isChecked, setIsChecked] = useState(false);
 
   const onChange = () => {
@@ -20,6 +25,4 @@ const CheckboxWithLabel = ({labelRef, inputRef, labelOn, labelOff}) => {
       {isChecked ? labelOn : labelOff}
     </label>
   );
-};
-
-export default CheckboxWithLabel;
+}

examples/react/__tests__/CheckboxWithLabel-test.js

@@ -1,6 +1,6 @@
 // Copyright 2004-present Facebook. All Rights Reserved.
 
-import React, {createRef} from 'react';
+import {createRef} from 'react';
 
 import * as TestUtils from 'react-dom/test-utils';
 import CheckboxWithLabel from '../CheckboxWithLabel';

examples/snapshot/.babelrc.js

@@ -1,6 +1,8 @@
 // Copyright (c) 2014-present, Facebook, Inc. All rights reserved.
 
 module.exports = {
-  presets: ['@babel/preset-env', '@babel/preset-react'],
-  plugins: ['@babel/plugin-proposal-class-properties'],
+  presets: [
+    '@babel/preset-env',
+    ['@babel/preset-react', {runtime: 'automatic'}],
+  ],
 };

examples/snapshot/Clock.js

@@ -1,8 +1,8 @@
 // Copyright 2004-present Facebook. All Rights Reserved.
 
-import React, {useEffect, useState} from 'react';
+import {useEffect, useState} from 'react';
 
-const Clock = () => {
+export default function Clock() {
   const [seconds, setSeconds] = useState(Date.now() / 1000);
 
   const tick = () => {
@@ -16,6 +16,4 @@ const Clock = () => {
   }, []);
 
   return <p>{seconds} seconds have elapsed since the UNIX epoch.</p>;
-};
-
-export default Clock;
+}

examples/snapshot/Link.js

@@ -1,13 +1,13 @@
 // Copyright 2004-present Facebook. All Rights Reserved.
 
-import React, {useState} from 'react';
+import {useState} from 'react';
 
 const STATUS = {
   HOVERED: 'hovered',
   NORMAL: 'normal',
 };
 
-const Link = ({page, children}) => {
+export default function Link({page, children}) {
   const [status, setStatus] = useState(STATUS.NORMAL);
 
   const onMouseEnter = () => {
@@ -28,6 +28,4 @@ const Link = ({page, children}) => {
       {children}
     </a>
   );
-};
-
-export default Link;
+}

examples/snapshot/__tests__/clock.test.js

@@ -2,7 +2,6 @@
 
 'use strict';
 
-import React from 'react';
 import Clock from '../Clock';
 import renderer from 'react-test-renderer';