The secret to getting Jest to work with ES Modules

I’m embarrassed for you, Jest. You’re a fantastic testing framework, but you’ve been achingly slow to embrace ES modules. It’s 2025 and everyone else has moved on to modern JavaScript syntax. You’re still using CommonJS. You know - require and module.exports. Devs are laughing at you behind your back.

If you fellow devs want to use ES modules in Jest, here are the secrets to getting Jest to work with ES modules.

ES Modules in Jest

Let’s say you have this function to test:

// sum.js
export const sum = (a, b) => a + b;

So you write a test like this:

// sum.test.js
import { sum } from "./sum.js";  // <-- this is the problem

test("adds numbers", () => {
  expect(sum(2, 3)).toBe(5);
});

Jest will throw errors like:

SyntaxError: Cannot use import statement outside a module

or

TypeError: Jest encountered an unexpected token

The solution is to run Jest with ES modules enabled. But you can only do that by explicitly running node with the --experimental-vm-modules flag. So in package.json, you need to add a script like this:

{
  ...
  "scripts": {
    "test": "node --experimental-vm-modules ./node_modules/.bin/jest"
  }
  ...
}

Test that on your Mac/Linux machine and it’ll work perfectly.

If the solution breaks in Windows 💩

Run this on Windows and you may see this error:

basedir=$(dirname "$(echo "$0" | sed -e 's,\\,/,g')")
          ^^^^^^^

SyntaxError: missing ) after argument list

If you see this, it’s because node_modules/.bin/jest is a Unix shell script. Windows doesn’t understand bash scripts.

The Quick Fix

You can make it work by using npx. Run this in a terminal window:

 npx --node-options="--experimental-vm-modules" jest

But this is a kludge.

The proper fix

The robust fix is to update your package.json to use this script:

{
  ...
  "scripts": {
    "test": "node --experimental-vm-modules ./node_modules/jest/bin/jest"
  },
  ...
}

All we’ve done here is tell the system to run the actual Jest as opposed to a Unix shell script that Windows can’t understand.

This totally works on both Windows and Unix systems. You’re welcome. 🙂

Now, Jest, we’re putting you on blast: you’ve got to do better!