Fix “Cannot use import statement outside a module” in Jest

 🧨 The Error

You're using ES modules (import/export) in your code or test files, and you run:

npm test

Only to see this:

SyntaxError: Cannot use import statement outside a module

✅ Why it Happens

Jest runs on Node.js, and by default, it expects CommonJS (require/module.exports) syntax.

If you're using import in your test or source files, Jest needs to know:

• You're using ES Modules (ESM)
• How to load and execute ESM correctly, especially in sandboxed environments

🛠 The Quick Fix (No Babel Needed)

1️⃣ Tell Node your project uses ES modules

In your package.json:

{

  "type": "module",

  "scripts": {

    "test": "node --experimental-vm-modules node_modules/jest/bin/jest.js"

  }

}

✅ "type": "module" enables import/export
✅ --experimental-vm-modules tells Node to allow ESM in Jest's sandbox

2️⃣ Create jest.config.js using ESM

// jest.config.js
export default {
  testEnvironment: 'node', // or 'jsdom' if you're testing DOM
};

✅ export default is needed because you're in ESM mode now
❌ module.exports = {} will fail here

🔍 Bonus: Why --experimental-vm-modules?

Jest uses Node's vm module internally to run your tests in isolated environments.

But vm doesn’t fully support import/export without this flag.

--experimental-vm-modules unlocks that ESM support, allowing Jest to handle import syntax cleanly. 

🧪 Alternative: Babel (if you want to go that route)

If you don’t want the --experimental flag in production setups, you can:

• Use Babel to transpile ES modules to CommonJS

• Tell Jest to load the transpiled version

But that adds build tooling complexity. For most projects, the solution above is simpler and more native.

---

✅ Final Project Checklist

• ✅ "type": "module" in package.json

• ✅ Custom test command using --experimental-vm-modules

• ✅ ESM-friendly jest.config.js

• ✅ All code uses import/export