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I'm attempting to test a React component with Jest/Enzyme while using Webpack.
I have a very simple test @
import React from 'react'; import { shallow } from 'enzyme'; import App from './App'; it('App', () => { const app = shallow(<App />); expect(1).toEqual(1); }); The relative component it's picking up is :
import React, { Component } from 'react'; import { render } from 'react-dom'; // import './styles/normalize.css'; class App extends Component { render() { return ( <div>app</div> ); } } render(<App />, document.getElementById('app')); However, running jest causes a failure:
Invariant Violation: _registerComponent(...): Target container is not a DOM element.
With errors @
at Object.<anonymous> (src/App.js:14:48) at Object.<anonymous> (src/App.test.js:4:38)
The test files references line 4, which is the import of <App />, that causes a fail. The stack trace says line 14 of App.js is the reason for the failure -- which is nothing more than the render call from react-dom, something I've never had a challenge with (the app renders properly from my Webpack setup).
For those interested (Webpack code):
module.exports = { entry: './src/App', output: { filename: 'bundle.js', path: './dist' }, module: { loaders: [ { test: /\.js?$/, exclude: /node_modules/, loader: 'babel', query: { presets: ['react', 'es2015'] } }, { test: /\.css$/, loader: 'style!css-loader?modules&importLoaders=1&localIdentName=[name]__[local]___[hash:base64:5]' }, { test: /\.scss$/, loader: 'style!css-loader?modules&importLoaders=1&localIdentName=[name]__[local]___[hash:base64:5]!sass' } ] } } And my package.json:
{ "name": "tic-tac-dux", "version": "1.0.0", "description": "", "main": "index.js", "scripts": { "dev": "webpack-dev-server --devtool eval --progress --colors --inline --hot --content-base dist/", "test": "jest" }, "jest": { "moduleNameMapper": { "^.+\\.(jpg|jpeg|png|gif|eot|otf|webp|svg|ttf|woff|woff2|mp4|webm|wav|mp3|m4a|aac|oga)$": "<rootDir>/__mocks__/fileMock.js", "^.+\\.(css|sass)$": "<rootDir>/__mocks__/styleMock.js" } }, "keywords": [], "author": "", "license": "ISC", "devDependencies": { "babel-core": "^6.17.0", "babel-jest": "^16.0.0", "babel-loader": "^6.2.5", "babel-polyfill": "^6.16.0", "babel-preset-es2015": "^6.16.0", "babel-preset-react": "^6.16.0", "css-loader": "^0.25.0", "enzyme": "^2.4.1", "jest": "^16.0.1", "jest-cli": "^16.0.1", "node-sass": "^3.10.1", "react-addons-test-utils": "^15.3.2", "react-dom": "^15.3.2", "sass-loader": "^4.0.2", "style-loader": "^0.13.1", "webpack": "^1.13.2", "webpack-dev-server": "^1.16.2" }, "dependencies": { "react": "^15.3.2", "react-dom": "^15.3.2" } } Oh, and if anyone is going to say that the div element isn't being loaded before the script, here's my index.html:
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>App</title> </head> <body> <div id="app"></div> <script src="/bundle.js"></script> </body> </html> What could be the reason for this peculiar rendering problem? Something to do with a new Jest update to 15.0?
751
React implements a browser-independent DOM system for performance and cross-browser compatibility.
The react-dom package provides DOM-specific methods that can be used at the top level of your app and as an escape hatch to get outside the React model if you need to.
React will assign the current property with the DOM element when the component mounts, and assign it back to null when it unmounts.
Deprecations. react-dom : ReactDOM.render has been deprecated. Using it will warn and run your app in React 17 mode.
For anyone else that was combing through the internet like I've been - looking for a solution to this when testing with Jest - I will back up the answer by @biphobe by saying Jest will cause this error to occur when you export something inside the same file that is calling ReactDOM.render.
In my case, I was exporting an object within my index.js where I was also calling ReactDOM.render. I removed this export and voila!
178
App.jsx is supposed to export the App class and do nothing more, render should be called elsewhere.
If you remove the render call from the App.jsx error should disappear, it pops up because the test environment doesn't supply the DOM with an app id.
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