Configure Jest for Angular

Question

According to various guides on the web configuring Jest for Angular is as easy as this:

ng new jest-test
cd jest-test
npm i -D jest jest-preset-angular

Modify package.json:

"test": "jest",
[...]
"jest": {
    "preset": "jest-preset-angular",
    "setupTestFrameworkScriptFile": "./src/setup-jest.ts"
},

setup-jest.ts:

import 'jest-preset-angular';

When running npm test I keep running into this error, though:

Jest encountered an unexpected token

This usually means that you are trying to import a file which Jest cannot parse, e.g. it's not plain JavaScript.

By default, if Jest sees a Babel config, it will use that to transform your files, ignoring "node_modules".

Here's what you can do:
 • 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/en/configuration.html

Details:

jest-test/src/app/app.component.spec.ts:1
({"Object.<anonymous>":function(module,exports,require,__dirname,__filename,global,jest){import { TestBed, async } from '@angular/core/testing';
                                                                                                ^

SyntaxError: Unexpected token {

  at ScriptTransformer._transformAndBuildScript (node_modules/jest-runtime/build/script_transformer.js:403:17)

I have tried countless variations of configuring the app that I found on th e web, all yielding this error message.

Let me know if I need to supply additional information.

Answer 1

If you use Angular CLI this library would be very helpful.
It will allow you to keep your workspace clear of boilerplate code related to Jest setup and also run your tests with Angular CLI (ng test).
This will also save you the trouble of configuring Jest.

As for your specific error, it is most probably related to your tsconfig.spec.json. Have you changed the module field to commonjs? This is required to make Jest work.

For more details read this article.

Disclaimer: I'm the owner of this library.