Unexpected token 'import' error while running Jest tests?

Question

I realize this question has been asked several times but all of the solutions I've come across don't seem to work for me. I'm running into the following error while trying to run Jest tests for a Vue app.

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://facebook.github.io/jest/docs/en/configuration.html

Details:

/node_modules/vue-awesome/icons/expand.js:1
({"Object.<anonymous>":function(module,exports,require,__dirname,__filename,global,jest){import Icon from '../components/Icon.vue'
                                                                                         ^^^^^^

SyntaxError: Unexpected token import

> 17 | import 'vue-awesome/icons/expand'

.babelrc:

{
  "presets": [
    ["env", {
      "modules": false,
      "targets": {
        "browsers": ["> 1%", "last 2 versions", "not ie <= 8"]
      }
    }]
  ],
  "env": {
    "test": {
      "presets": [
        ["env", { "targets": { "node": "current" }}]
      ]
    }
  }
}

jest config in package.json:

"jest": {
  "moduleFileExtensions": [
    "js",
    "vue"
  ],
  "moduleNameMapper": {
    "^@/(.*)$": "<rootDir>/src/$1"
  },
  "transform": {
    "^.+\\.js$": "<rootDir>/node_modules/babel-jest",
    ".*\\.(vue)$": "<rootDir>/node_modules/vue-jest"
  },
  "snapshotSerializers": [
    "<rootDir>/node_modules/jest-serializer-vue"
  ],
  "moduleDirectories": [
    "node_modules",
    "src"
  ]
}

It looks like the initial import in the script for the Vue component being mounted for the test is working but the import within the module itself (import Icon from '../components/Icon.vue) is not recognized.

boiler plate repo to re-creates the issue: github.com/DonaldPeat/stackoverflow-jest-question

How can I resolve this?

Answer 1

You just need to make sure that vue-awesome will be transformed by jest, so add following to your jest config:

transformIgnorePatterns: ["/node_modules/(?!vue-awesome)"],

which means: "Ignore everything in node_modules except for vue-awesome.

Also here is exhausive list of other issues that might cause this error: https://github.com/facebook/jest/issues/2081

Answer 2

If you are encountering this problem after updating to a newer Jest version, try clearing Jest's internal cache:

jest --clearCache

Answer 3

Adding this in the package.json works for me (replace <package_name> with causing package name)

"jest": {
    "transformIgnorePatterns": ["node_modules/(?!<package_name>)/"]
}

Answer 4

We had the same issue with another library. The root cause was that we had a circular dependency in code. But the error text did not refer to it at all. just like in this post: "Jest encountered an unexpected token..."

Answer 5

In my case I needed testEnvironment: "node" in jest.config.js file. The error came out when I started tests against Vue Router.

// jest.config.js
module.exports = {
  preset: "@vue/cli-plugin-unit-jest/presets/typescript",
  transform: {
    "^.+\\.vue$": "vue-jest",
    ".+\\.(css|styl|less|sass|scss|png|jpg|ttf|woff|woff2)$":
      "jest-transform-stub",
  },
  moduleNameMapper: {
    "^.+.(css|styl|less|sass|scss|png|jpg|ttf|woff|woff2)$":
      "jest-transform-stub",
  },
  testEnvironment: "node",  // It fixes my issue
};