Does Jest support ES6 import/export?

P.Brian.Mackey picture P.Brian.Mackey · Mar 2, 2016 · Viewed 34k times · Source

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

Paulo Coghi picture Paulo Coghi · Sep 7, 2018

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.