Configure Jest for ES Modules
Our application uses ES Modules, so configure Jest to run in ESM mode.
Update the package.json scripts.
The experimental VM modules flag is used by Jest for its native ESM support in this configuration.
Use a Jest release compatible with your Node.js version.
Alternative Testing Setup
If you prefer to avoid Jest's ESM configuration complexity, Node.js provides a built-in test runner through node:test.
package.json Test Configuration
{
"scripts": {
"start": "node src/server.js",
"dev": "node --watch src/server.js",
"test": "NODE_OPTIONS=--experimental-vm-modules jest --runInBand"
}
}Configures Jest to execute in ESM mode and runs tests sequentially. On Windows, use cross-env or a platform-specific environment variable command if required.
Key Takeaways
Jest requires ESM-compatible configuration.
The VM modules flag enables native ESM support in this setup.
Keep testing configuration separate from production scripts.