support testing with jest

[Julian-B90]

it is possible you can import the local from date-fns/locale?

Because we i run my JEST test i get this error:

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.
     • 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:

    /frontend/node_modules/date-fns/esm/locale/index.js:2
    export { default as af } from "./af/index.js";
    ^^^^^^

    SyntaxError: Unexpected token 'export'

      at Runtime.createScriptFromCode (node_modules/jest-runtime/build/index.js:1479:14)
      at node_modules/ngx-mat-datefns-date-adapter/bundles/ngx-mat-datefns-date-adapter.umd.js:2:191
      at Object.<anonymous> (node_modules/ngx-mat-datefns-date-adapter/bundles/ngx-mat-datefns-date-adapter.umd.js:5:2)

[sapozhnikovay]

Hello, @Julian-B90 ,

Could you please create a small reproduction repo or a Stackblitz ?

Also, I've looked through the Jest suggestions in the error message. have you tried disabling date-fns package from transformation via "transformIgnorePatterns" setting in Jest config?

[Julian-B90]

Hey @sapozhnikovay i have create a git repo. I hope it helps.

Wenn you run npm run test you get the error.

https://github.com/Julian-B90/angular-jest-reproduce-ngx-mat-datefns-date-adapter

[sapozhnikovay]

Thanks, Julian. I'll look into the issue and let you know.

[sapozhnikovay]

Julian,

Right now you can include date-fns ES Module into jest transforming process via configuration.
Set this into jest.config.ts :

   transformIgnorePatterns: ['node_modules/(?!@ngrx|date-fns)'],

And this into compilerOptions object in tsconfig.ts :

    "allowJs": true

In the repo provided above this settings lead to successful compilation process(at first run it takes time =) and subsequent error in the test itself (lack of various imports in the configureTestingModule for the ngx-mat-datefns-date-adapter).

I'll examine more thoroughly the ESM exports in the date-fns and update my package to use plain exports in a couple of days.

[Julian-B90]

@sapozhnikovay the options works thanks you. But you were right this test are now very slow.

[sapozhnikovay]

Fixed in version 11.2.2