We have Next.js application that uses the next/jest
configurator to set up jest in a good way for Next projects. Recently we added the @piwikpro/next-piwik-pro package to our app, as recommended by the Piwik docs. Tracking is working fine, but the integration tests are failing. The error message from Jest is
Test suite failed to run
Jest encountered an unexpected token
Jest failed to parse a file. This happens e.g. when your code or its dependencies use non-standard JavaScript syntax, or when Jest is not configured to support such syntax.
Out of the box Jest supports Babel, which will be used to transform your files into valid JS based on your Babel configuration.
By default "node_modules" folder is ignored by transformers.
Here's what you can do:
• If you are trying to use ECMAScript Modules, see https://jestjs.io/docs/ecmascript-modules for how to enable it.
• If you are trying to use TypeScript, see https://jestjs.io/docs/getting-started#using-typescript
• To have some of your "node_modules" files transformed, you can specify a custom "transformIgnorePatterns" in your config.
• If you need a custom transformation specify a "transform" option in your config.
• If you simply want to mock your non-JS modules (e.g. binary assets) you can stub them out with the "moduleNameMapper" config option.
You'll find more details and examples of these config options in the docs:
https://jestjs.io/docs/configuration
For information about custom transformations, see:
https://jestjs.io/docs/code-transformation
Details:
/...redacted... /node_modules/@piwikpro/next-piwik-pro/index.js:1
({"Object.<anonymous>":function(module,exports,require,__dirname,__filename,jest){import { PiwikProProvider, usePiwikPro } from './core';
It seems that the import statement from the next-piwik-pro package is not appreciated by jest, and that this occurs because node_modules are never transpiled when using next/jest.
I’m certainly not an expert in these matters, but would it be possible to include a commonjs build with the npm package? Or maybe there is another way to work around this?
I have tried several different approaches, including manipulating the the config generated from nextJest (failed because the return type not a basic object but something complicated with a bunch of async things) and running jest in ESM mode. Could not make any progress with that.