I'm trying to write a simple jest test for a 3rd party package were using that only exports an ES module. It's a wrapper around an http server.
Here is a test repo I setup (just run yarn && yarn jest to reproduce): https://github.com/jamesopti/hocuspocus-testing
No matter what config I experiment with, I still get this error when trying to run it:
Must use import to load ES Module: /Users/j/hocuspocus-testing/node_modules/@hocuspocus/server/dist/hocuspocus-server.esm.js
> 1 | import { Server, Hocuspocus } from '@hocuspocus/server'
| ^
2 | import * as request from 'supertest'
3 |
4 | describe('Server (e2e)', () => {
Things I've tried already:
The Jest instructions on ES modules: https://jestjs.io/docs/ecmascript-modules
In Jest configuration using transformIgnorePatterns
transformIgnorePatterns: ['node_modules/(?!@hocuspocus/)']Using Babel via babel-jest
modifying transform setup in Jest configuration as '^.+\.jsx?$': 'babel-jest', '^.+\.tsx?$': 'ts-jest'
Ran into the error You appear to be using a native ECMAScript module configuration file, which is only supported when running Babel asynchronously.
Using .babel.config.js instead of .babelrc.js
Any ideas what I'm missing here? I thought this would be straightforward
[EDIT 1] - Added tsconfig.json and a working src/index.ts file to the example repo.
You don't have a tsconfig.json file that specifies module. Therefore it uses the default, where it transpiles all your modules to CommonJS syntax, which uses require.
If you actually look at your dist/hocuspocus-server.esm.js, you should see it using require over the ESM import syntax.
So for anyone still hitting this, ESM configuration explained in this section of documentation :
https://kulshekhar.github.io/ts-jest/docs/guides/esm-support
{
// [...]
"jest": {
"extensionsToTreatAsEsm": [".ts"],
"globals": {
"ts-jest": {
"useESM": true
}
}
}
}
I was having the same problem with my svelte app and testing. I ultimately traced it to having a jest.config.js and a jest.config.json in my root folder. It seems that jest does not have automatic config file resolution and was using a default configuration instead of either of my specified configurations.