Compatibility of JavaScript test runners with "native" ES modules based spec files (`import`), without additional transpilation and plugins

updated: 2021-03-02

For node-based runners, assuming node or 12.17.0+ or 13.2.0+ (or v12.11.0+ with --experimental-modules command line flag)

`mocha` (node)

✅ .spec.mjs: supported, w/o additional conf
✅ .spec.js + "type": "module" in package.json: supported, w/o additional conf

Note: by default mocha looks for specs in /test/ folder.

Support added in mocha 7.1.0 (February 2020)

✅ .spec.mjs: supported since 3.6.2 (October 2020) docs
- (make sure to update "spec_files" field in jasmine.json to match .mjs
❌ .spec.js + "type": "module" in package.json: not supported yet, but there's a workaround

Note: you need to create a jasmine.json file (which by default lives in /spec/ folder); you can use jasmine init

❌ Not supported yet as of March 2021 (v6.1.1)

✅ Supported (I didn't test though)
🎄 Uses import maps for mocking ES modules which are normally immutable (hence not easily mockable, contrary to CJS exports)

esm node package can be used with mocha

Feel invited to add docs of your favorite test runner