To have some of your "node_modules" files transformed, you can specify a custom "transformIgnorePatterns" in your config

Question

I running jest test file and getting the following error:

 ● 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:

    /Users/test/dev/pm/client/node_modules/spacetime/src/index.js:1
    ({"Object.<anonymous>":function(module,exports,require,__dirname,__filename,jest){import Spacetime from './spacetime.js'
                                                                                      ^^^^^^

    SyntaxError: Cannot use import statement outside a module

       6 | import search from '../../assets/images/search.svg';
       7 | import Dropdown from 'react-bootstrap/Dropdown';
    >  8 | import spacetime from "spacetime";
         | ^
       9 | import languages from "../../libraries/languages/language-list";
      10 | import { Rating } from 'react-simple-star-rating';
      11 |

      at Runtime.createScriptFromCode (node_modules/jest-runtime/build/index.js:1728:14)
      at Object.<anonymous> (src/components/Mentor/MentorList.js:8:1)

Test Suites: 1 failed, 1 total
Tests:       0 total
Snapshots:   0 total
Time:        2.097 s

I tried to fix it by adding the following to package.json, but that didn't work:

  "jest": {
    "transformIgnorePatterns": [
      "node_modules/(?!spacetime)"
    ]
  },

Can someone please help?

Answer 1

spacetime package main file is ES6 module. See node_modules/spacetime/src/index.js, this is the main file the package exports.The package.json of spacetime include "main": "src/index.js".

By default "node_modules" folder is ignored by transformers.

You don't need to add transformIgnorePatterns configuration for jest config, the node_modules folder is ignored by transformers.

But this is not the issue.

The issue is jest does not parse es6 import/export statement by default, even though it uses babel.

Out of the box Jest supports Babel, which will be used to transform your files into valid JS based on your Babel configuration.

We need to transform the es6 import and export syntax.

option 1. Add babel config

option 2. Use ts-jest preset for jest.

jest.config.js:

module.exports = {
  preset: 'ts-jest/presets/js-with-ts',
  testEnvironment: 'jsdom'
};

option 3. Use esbuild-jest

jest.config.js:

module.exports = {
  testEnvironment: 'jsdom',
  transform: {
    '\\.[jt]sx?$': 'esbuild-jest',
  },
};