I'm recently learning how to write component tests with jest and the react testing library.
I have an animation in useLayoutEffect, the code works fine on the browser but has error in jest, the code and error message are as follows
Progress/index.tsx
import React, { useRef, useState, useLayoutEffect, useEffect } from "react"
import { useCarousel, useCarouselDispatch } from "../../store/AppContext"
import { ECarouselActionType } from '../../store/types'
import "./styles.css"
export default function Progress( { pid }: { pid: number}) {
const { progressId } = useCarousel()
const dispatch = useCarouselDispatch()
const inner = useRef<HTMLDivElement>(null)
useLayoutEffect(()=>{
if (pid === progressId) {
const keyframes = new KeyframeEffect(
inner.current,
[
{ transform: 'scaleX(0%)', transformOrigin: 'left center' },
{ transform: 'scaleX(100%)', transformOrigin: 'left center' }
],
{ duration: 3000, fill: 'forwards' }
);
const anim = new Animation(keyframes, document.timeline);
anim.play()
const finish = anim.finished
finish.then(() => {
dispatch({
type: ECarouselActionType.SET_MOVE
})
})
}
}, [progressId])
return (
<div className="Progress">
<div className="progress-wrap">
<div className="progress-bar progress-outer">
<div
className="progress-bar progress-inner"
ref={inner}
style={{ background: pid === progressId ? '#fff' : '#9aa0a6'}}
>
</div>
</div>
</div>
</div>
)
}
App.test.tsx // Not the actual test case, just to see the test running process
/**
* @jest-environment jsdom
*/
import React from 'react';
import '@testing-library/jest-dom';
import { render } from '@testing-library/react';
import App from './App';
test('renders learn react link', () => {
const { getByText } = render(<App />);
const linkElement = getByText(/Tablet/i);
expect(linkElement).toBeInTheDocument();
});
setupTests.ts
// jest-dom adds custom jest matchers for asserting on DOM nodes.
// allows you to do things like:
// expect(element).toHaveTextContent(/react/i)
// learn more: https://github.com/testing-library/jest-dom
import '@testing-library/jest-dom';
package.json // create-react-app eject
{
"name": "react-assignment",
"version": "0.1.0",
"private": true,
"dependencies": {
"jest-environment-jsdom": "^27.0.6",
"@babel/core": "^7.16.0",
"@pmmmwh/react-refresh-webpack-plugin": "^0.5.3",
"@svgr/webpack": "^5.5.0",
"babel-jest": "^27.4.2",
"babel-loader": "^8.2.3",
"babel-plugin-named-asset-import": "^0.3.8",
"babel-preset-react-app": "^10.0.1",
"bfj": "^7.0.2",
"browserslist": "^4.18.1",
"camelcase": "^6.2.1",
"case-sensitive-paths-webpack-plugin": "^2.4.0",
"css-loader": "^6.5.1",
"css-minimizer-webpack-plugin": "^3.2.0",
"dotenv": "^10.0.0",
"dotenv-expand": "^5.1.0",
"eslint": "^8.3.0",
"eslint-config-react-app": "^7.0.0",
"eslint-webpack-plugin": "^3.1.1",
"file-loader": "^6.2.0",
"fs-extra": "^10.0.0",
"html-webpack-plugin": "^5.5.0",
"identity-obj-proxy": "^3.0.0",
"jest": "^27.4.3",
"jest-resolve": "^27.4.2",
"jest-watch-typeahead": "^1.0.0",
"mini-css-extract-plugin": "^2.4.5",
"postcss": "^8.4.4",
"postcss-flexbugs-fixes": "^5.0.2",
"postcss-loader": "^6.2.1",
"postcss-normalize": "^10.0.1",
"postcss-preset-env": "^7.0.1",
"prompts": "^2.4.2",
"react": "^17.0.2",
"react-app-polyfill": "^3.0.0",
"react-dev-utils": "^12.0.0",
"react-dom": "^17.0.2",
"react-refresh": "^0.11.0",
"resolve": "^1.20.0",
"resolve-url-loader": "^4.0.0",
"sass-loader": "^12.3.0",
"semver": "^7.3.5",
"source-map-loader": "^3.0.0",
"style-loader": "^3.3.1",
"tailwindcss": "^3.0.2",
"terser-webpack-plugin": "^5.2.5",
"webpack": "^5.64.4",
"webpack-dev-server": "^4.6.0",
"webpack-manifest-plugin": "^4.0.2",
"workbox-webpack-plugin": "^6.4.1"
},
"devDependencies": {
"@testing-library/jest-dom": "^5.16.1",
"@testing-library/react": "^12.1.2",
"@testing-library/user-event": "^13.5.0",
"@types/jest": "^27.4.0",
"@types/node": "^17.0.13",
"@types/react": "^17.0.38",
"@types/react-dom": "^17.0.11",
"typescript": "^4.5.5"
},
"scripts": {
"start": "node scripts/start.js",
"build": "node scripts/build.js",
"test": "node scripts/test.js"
},
"eslintConfig": {
"extends": "react-app"
},
"browserslist": {
"production": [
">0.2%",
"not dead",
"not op_mini all"
],
"development": [
"last 1 chrome version",
"last 1 firefox version",
"last 1 safari version"
]
},
"jest": {
"roots": [
"<rootDir>/src"
],
"collectCoverageFrom": [
"src/**/*.{js,jsx,ts,tsx}",
"!src/**/*.d.ts"
],
"setupFiles": [
"react-app-polyfill/jsdom"
],
"setupFilesAfterEnv": [
"<rootDir>/src/setupTests.ts"
],
"testMatch": [
"<rootDir>/src/**/__tests__/**/*.{js,jsx,ts,tsx}",
"<rootDir>/src/**/*.{spec,test}.{js,jsx,ts,tsx}"
],
"testEnvironment": "jsdom",
"transform": {
"^. \\.(js|jsx|mjs|cjs|ts|tsx)$": "<rootDir>/config/jest/babelTransform.js",
"^. \\.css$": "<rootDir>/config/jest/cssTransform.js",
"^(?!.*\\.(js|jsx|mjs|cjs|ts|tsx|css|json)$)": "<rootDir>/config/jest/fileTransform.js"
},
"transformIgnorePatterns": [
"[/\\\\]node_modules[/\\\\]. \\.(js|jsx|mjs|cjs|ts|tsx)$",
"^. \\.module\\.(css|sass|scss)$"
],
"modulePaths": [],
"moduleNameMapper": {
"^react-native$": "react-native-web",
"^. \\.module\\.(css|sass|scss)$": "identity-obj-proxy"
},
"moduleFileExtensions": [
"web.js",
"js",
"web.ts",
"ts",
"web.tsx",
"tsx",
"json",
"web.jsx",
"jsx",
"node"
],
"watchPlugins": [
"jest-watch-typeahead/filename",
"jest-watch-typeahead/testname"
],
"resetMocks": true
},
"babel": {
"presets": [
"react-app"
]
}
}
Running yarn test shows the following error
FAIL src/App.test.tsx
✕ renders learn react link (46 ms)
● renders learn react link
ReferenceError: KeyframeEffect is not defined
10 | useLayoutEffect(()=>{
11 | if (pid === progressId) {
> 12 | const keyframes = new KeyframeEffect(
| ^
13 | inner.current,
14 | [
15 | { transform: 'scaleX(0%)', transformOrigin: 'left center' },
at src/components/Progress/index.tsx:12:25
Any idea how to fix this?
CodePudding user response：
You got this error because jest is not using an actual browser when running test, but a NodeJS environment with jest-dom, which is a mock of many browser feature but unfortunately does not provide the class KeyframeEffect.
You can either mock the KeyframeEffect by yourself
window.KeyframeEffect = class KeyframeEffect {
// mock class methods here
}
Or prevent this code to be executed in an environment where KeyframeEffect does not exist, example: old browser or testing
useLayoutEffect(() => {
if (pid === progressId && window.KeyframeEffect) {