Jest: node.js SyntaxError: Cannot use import statement outside a module

Question

I have just started learning jest testing and created a sample application to get familiar with jest testing. However, I am getting following error...

Language.js

const calculateTip = (total, percentage) => {
    return total + ((percentage / 100) * total) + 1;
};

export {
    calculateTip,
}

package.json

{
    "dependencies": {
        "express": "^4.18.2"
    },
    "type": "module",
    "main": "src/app.js",
    "scripts": {
        "start": "node src/app.js",
        "test": "cls && env-cmd -f ./envs/test.env jest --watchAll"
    },
    "devDependencies": {
        "env-cmd": "^10.1.0",
        "jest": "^29.2.2",
        "supertest": "^6.3.1"
    }
}

I have tried googling for the solution but no luck so far.

nana · Accepted Answer · 2023-04-24 12:48:12Z

9

Jest now ships with experimental support for ECMAScript Modules (ESM):

https://jestjs.io/docs/ecmascript-modules

The simplest way forward is to update your test script to execute node with --experimental-vm-modules e.g.

node --experimental-vm-modules node_modules/jest/bin/jest.js

or to add an environment variable to the test script

NODE_OPTIONS=--experimental-vm-modules npx jest

See the link above for more details.

edited Apr 24, 2023 at 12:48

nana

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answered Apr 24, 2023 at 3:00

Callum

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1 Comment

D_S_toowhite Over a year ago

The solution is correct. Just to add, in Windows to set NODE_OPTIONS env you may want to use this package: github.com/kentcdodds/cross-env

felixmosh · Accepted Answer · 2022-11-02 12:56:55Z

8

Node.js supports esm syntax only from v16, but jest doesn't support it yet. Therefore, you have 2 choices:

Don't use the esm syntax (import / export)
Add jest-babel with it's config to transpile (convert) esm syntax to cjs one.

answered Nov 2, 2022 at 12:56

felixmosh

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1 Comment

Mr.Singh Over a year ago

Thank you @felixmosh, Although this worked, there are so many depreciation warnings while installing the packages. I had to delete the node_modules directory and install the package before running the npm install command.

Exodus Reed · Accepted Answer · 2023-01-31 11:25:19Z

3

You can fix it by installing jest-babel and then creating babel.config.cjs in your root directory and pasting the following into it:

//babel.config.cjs
module.exports = {
  presets: [
    [
      '@babel/preset-env',
      {
        targets: {
          node: 'current',
        },
      },
    ],
  ],
};

...
//package.json
"type": "module"

//tsconfig.json
...
"target": "esnext", 
"module": "commonjs", 
...

answered Jan 31, 2023 at 11:25

Exodus Reed

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2 Comments

PlexQ Over a year ago

This did not work for me.

wristbands Over a year ago

You must also make sure that all javascript files in your project end in .js, not .mjs. Otherwise babel won't transpile the file and you'll get errors.

Smart Coder · Accepted Answer · 2023-07-14 18:11:35Z

0

Add this to you package.json in scripts:

"test": "cross-env NODE_OPTIONS=--experimental-vm-modules npx jest"

when you run 'npm test', it'll trigger above. 'cross-env' is added so it will run in any shell otherwise not needed in bash.

If you're in bash, then just run 'NODE_OPTIONS=--experimental-vm-modules npx jest'

answered Jul 14, 2023 at 18:11

Smart Coder

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