Does Jest support ES6 import/export? - ecmascript-6

Question

If I use import/export from ES6 then all my Jest tests fail with error:
Unexpected reserved word
I convert my object under test to use old school IIFE syntax and suddenly my tests pass. Or, take an even simpler test case:
var Validation = require('../src/components/validation/validation'); // PASS
//import * as Validation from '../src/components/validation/validation' // FAIL
Same error. Obviously there's a problem with import/export here. It's not practical for me to rewrite my code using ES5 syntax just to make my test framework happy.
I have babel-jest. I tried various suggestions from GitHub issues. It is no go so far.
File package.json
"scripts": {
"start": "webpack-dev-server",
"test": "jest"
},
"jest": {
"testPathDirs": [
"__tests__"
],
"testPathIgnorePatterns": [
"/node_modules/"
],
"testFileExtensions": ["es6", "js"],
"moduleFileExtensions": ["js", "json", "es6"]
},
File babelrc
{
"presets": ["es2015", "react"],
"plugins": ["transform-decorators-legacy"]
}
Is there a fix for this?

Answer 1

From my answer to another question, this can be simpler:
The only requirement is to configure your test environment to Babel, and add the ECMAScript 6 transform plugin:
Step 1:
Add your test environment to .babelrc in the root of your project:
{
"env": {
"test": {
"plugins": ["#babel/plugin-transform-modules-commonjs"]
}
}
}
Step 2:
Install the ECMAScript 6 transform plugin:
npm install --save-dev #babel/plugin-transform-modules-commonjs
And that's it. Jest will enable compilation from ECMAScript modules to CommonJS automatically, without having to inform additional options to your jest property inside package.json.

Answer 2

UPDATE 2020 - native support of ECMAScript modules (ESM)
According to this issue, there is native support of ESM from jest#25.4.0. So you won't have to use babel anymore. At the time of writing this answer (05/2020), to activate that you need to do three simple things:
Make sure you don't transform away import statements by setting transform: {} in config file
Run node#^12.16.0 || >=13.2.0 with --experimental-vm-modules flag
Run your test with jest-environment-node or jest-environment-jsdom-sixteen.
So your Jest configuration file should contain at least this:
export default {
testEnvironment: 'jest-environment-node',
transform: {}
...
};
And to set --experimental-vm-modules flag, you will have to run Jest as follows:
node --experimental-vm-modules node_modules/jest/bin/jest.js
Also note in the Github issue that this approach does not yet support the jest object. So you may need to import it manually:
import {jest} from '#jest/globals'
(I hope this will change in the future)

Answer 3

For an updated configuration, I'm using https://babeljs.io/setup#installation
Select JEST and be happy:
As a reference, the current configuration:
npm install --save-dev babel-jest
In your package.json file, make the following changes:
{
"scripts": {
"test": "jest"
},
"jest": {
"transform": {
"^.+\\.jsx?$": "babel-jest"
}
}
}
Install babel preset:
npm install #babel/preset-env --save-dev
Create a .babelrc file:
{
"presets": ["#babel/preset-env"]
}
Run your tests:
npm run test

Answer 4

In package.json, kindly set like this one: "test": "node --experimental-vm-modules node_modules/.bin/jest"
Should be good!

Answer 5

It's a matter of adding stage-0 to your .babelrc file. Here is an example:
{
"presets": ["es2015", "react", "stage-0"],
"plugins": ["transform-decorators-legacy"]
}

Answer 6

I encountered the same issue.
These are what I did:
yarn add --dev babel-jest #babel/core #babel/preset-env
Make file jest.config.js in rootDir.
module.exports = {
moduleFileExtensions: ["js", "json", "jsx", "ts", "tsx", "json"],
transform: {
'^.+\\.(js|jsx)?$': 'babel-jest'
},
testEnvironment: 'node',
moduleNameMapper: {
'^#/(.*)$': '<rootDir>/$1'
},
testMatch: [
'<rootDir>/**/*.test.(js|jsx|ts|tsx)', '<rootDir>/(tests/unit/**/*.spec.(js|jsx|ts|tsx)|**/__tests__/*.(js|jsx|ts|tsx))'
],
transformIgnorePatterns: ['<rootDir>/node_modules/']
};
Then make file babal.config.js in rootDir.
Go like this:
module.exports = {
"presets": ["#babel/preset-env"]
}

Answer 7

Below is how I setup jest, typescript and ES Modules for my project.
jest.config.js
/**
* #type {import('ts-jest/dist/types').InitialOptionsTsJest}
* To configure ESM support, see: https://kulshekhar.github.io/ts-jest/docs/guides/esm-support
*
**/
export default {
preset: 'ts-jest/presets/default-esm',
testEnvironment: 'node',
extensionsToTreatAsEsm: ['.ts'],
globals: {
'ts-jest': {
useESM: true
}
},
setupFiles: ['<rootDir>/__tests__/setup.ts'],
};
tsconfig.json
{
"compilerOptions": {
"target": "ESNext",
"module": "ESNext",
"outDir": "./dist",
"moduleResolution": "node",
// "strict": true,
"esModuleInterop": true,
"inlineSourceMap": true,
}
}
package.json scripts and devDependencies
"scripts": {
"start": "node ./dist/server.js",
"dev": "tsc-watch --onSuccess \"node ./dist/server.js\"",
"test": "cross-env NODE_OPTIONS=--experimental-vm-modules jest"
},
"devDependencies": {
"#jest/globals": "^27.4.4",
"#types/express": "^4.17.13",
"#types/jest": "^27.4.0",
"#types/supertest": "^2.0.11",
"cross-env": "^7.0.3",
"supertest": "^6.2.1",
"ts-jest": "^27.1.3"
}
__tests__/setup.ts
import dotenv from 'dotenv';
dotenv.config({
path: './.env.test'
});

Answer 8

all is explained in the jest docs: jest docs
1.
npm install --save-dev babel-jest #babel/core #babel/preset-env
in file: babel.config.js
module.exports = {
presets: [['#babel/preset-env', {targets: {node: 'current'}}]],
};

Answer 9

In addition to installing babel-jest (which comes with Jest by default now) be sure to install regenerator-runtime.

Answer 10

To add support for React and react-testing-library it may be useful to eject CreateReactApp and take all needed Jest configuration from the package.json. It is ready to use with another bundler, Rollup in my case.