Example doesn't work

Hi, I’ve cloned repository. Installed dependencies in example folder. And when running yarn test I get:

Validation Error:

Module jest-preset-angular should have "jest-preset.js" or "jest-preset.json" file at the root.

I see that this file is in root. I’ve also copied it to example folder and example/src but same error appears.

[thymikee]

have you run yarn in both root and example/ directories?

[wtho]

• Works with yarn

  yarn install
  cd example
  yarn install
  yarn test
  

• Does not work with npm by default

  npm install
  cd example
  npm install
  npm test
  

  Something like this will come up:

    ● Test suite failed to run
    Cannot find module 'core-js/es6/reflect' from 'setupJest.js'
  

The reason is the symlink strategy by npm. In the example folder itself peerDependencies like @angular/... or core-js are installed, but not in the root folder of the library. We do not need them there to publish and test the library.

When resolving dependencies, npm will only go UP and look for node_modules folders.

As the symlink created by npm links upwards to ../, and as core-js is referenced in the preset in the parent folder, it will start to look for this dependency in the root folder <repo>/node_modules and upwards, but not in <repo>/example/node_modules. But it is not installed there.

yarn handles the sitation different. It actually copies the whole parent folder into <repo>/example/node_modules/jest-preset-angular and therefore require('core-js') in the preset can find the dependency in `<repo>/example/node_modules/core-js.

There are four solutions if you want to try out the example app:

• use yarn (install it using npm i -g yarn)
• install a jest-preset-angular version from npm, as @webdevelopland suggested using npm i -D jest-preset-angular@latest
• copy the root folder manually into example/node_modules using from inside example:

  rm node_modules/jest-preset-angular
  mkdir node_modules/jest-preset-angular
  cp -r ../AngularSnapshotSerializer.js ../HTMLCommentSerializer.js ../index.js ../InlineHtmlStripStylesTransformer.js ../jest-preset.js ../package.json ../setupJest.js ../zone-patch  node_modules/jest-preset-angular