Jest fails with "Unexpected token *" on import statement

javascript typescript jestjs
Top-Master picture Top-Master · Apr 22, 2019 · Viewed 48.5k times · Source

Why does Jest fail with "Unexpected token *" on a simple import statement...

Error log:

Admin@Admin-PC MINGW32 /d/project (master)
$ npm run test

> [email protected] test D:\project
> jest

FAIL __tests__/App-test.tsx
  ? Test suite failed to run

    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:

    D:\project\node_modules\react-navigation-tabs\src\navigators\createBottomTabNavigator.js:3
    import * as React from 'react';
           ^

    SyntaxError: Unexpected token *

      14 | // );
      15 |
    > 16 | export default createBottomTabNavigator({
         |                ^
      17 |   map: {
      18 |     screen: MapView,
      19 |     navigationOptions: {

      at ScriptTransformer._transformAndBuildScript (node_modules/@jest/transform/build/ScriptTransformer.js:471:17)
      at ScriptTransformer.transform (node_modules/@jest/transform/build/ScriptTransformer.js:513:25)
      at Object.get createBottomTabNavigator [as createBottomTabNavigator] (node_modules/react-navigation-tabs/src/index.js:9:12)
      at Object.<anonymous> (src/app/main.view.tsx:16:16)

FAIL src/component/reinput/example/__tests__/index.ios.js (19.352s)
  ? Console

    console.error node_modules/react-native/Libraries/YellowBox/YellowBox.js:59
      Warning: React.createElement: type is invalid -- expected a string (for built-in components) or a class/function (for composite components) but got: object. You likely forgot to export your component from the file it's defined in, or you might have mixed up default and named imports.

  ? renders correctly

    Invariant Violation: Element type is invalid: expected a string (for built-in components) or a class/function (for composite components) but got: object. You likely forgot to export your component from the file it's defined in, or you might have mixed up default and named imports.

      at invariant (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:55:15)
      at createFiberFromTypeAndProps (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:2054:11)
      at createFiberFromElement (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:2075:15)
      at reconcileSingleElement (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:4605:23)
      at reconcileChildFibers (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:4662:35)
      at reconcileChildren (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:6329:28)
      at updateHostRoot (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:6741:5)
      at beginWork (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:7566:14)
      at performUnitOfWork (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:11234:12)
      at workLoop (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:11266:24)

FAIL src/component/reinput/example/__tests__/index.android.js (19.365s)
  ? Console

    console.error node_modules/react-native/Libraries/YellowBox/YellowBox.js:59
      Warning: React.createElement: type is invalid -- expected a string (for built-in components) or a class/function (for composite components) but got: object. You likely forgot to export your component from the file it's defined in, or you might have mixed up default and named imports.

  ? renders correctly

    Invariant Violation: Element type is invalid: expected a string (for built-in components) or a class/function (for composite components) but got: object. You likely forgot to export your component from the file it's defined in, or you might have mixed up default and named imports.

      at invariant (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:55:15)
      at createFiberFromTypeAndProps (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:2054:11)
      at createFiberFromElement (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:2075:15)
      at reconcileSingleElement (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:4605:23)
      at reconcileChildFibers (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:4662:35)
      at reconcileChildren (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:6329:28)
      at updateHostRoot (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:6741:5)
      at beginWork (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:7566:14)
      at performUnitOfWork (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:11234:12)
      at workLoop (node_modules/react-test-renderer/cjs/react-test-renderer.development.js:11266:24)

Test Suites: 3 failed, 3 total
Tests:       2 failed, 2 total
Snapshots:   0 total
Time:        22.774s
Ran all test suites.
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! [email protected] test: `jest`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the [email protected] test script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     C:\Users\Admin\AppData\Roaming\Roaming\npm-cache\_logs\2019-04-22T11_52_36_984Z-debug.log

package.json file:

{
  "name": "MyApp",
  "version": "0.0.1",
  "private": true,
  "scripts": {
    "start": "node node_modules/react-native/local-cli/cli.js start",
    "test": "jest"
  },
  "dependencies": {
    "react": "16.8.3",
    "react-native": "0.59.4",
    "react-native-gesture-handler": "^1.1.0",
    "react-native-reanimated": "^1.0.1",
    "react-native-splash-screen": "^3.2.0",
    "react-navigation": "^3.8.1",
    "react-navigation-tabs": "^2.1.1"
  },
  "devDependencies": {
    "@babel/core": "^7.4.3",
    "@babel/runtime": "^7.4.3",
    "@types/jest": "^24.0.11",
    "@types/react": "^16.8.13",
    "@types/react-dom": "^16.8.4",
    "@types/react-native": "^0.57.46",
    "@types/react-test-renderer": "^16.8.1",
    "babel-jest": "^24.7.1",
    "jest": "^24.7.1",
    "metro-react-native-babel-preset": "^0.53.1",
    "react-test-renderer": "16.8.3",
    "typescript": "^3.4.3"
  },
  "jest": {
    "preset": "react-native"
  }
}

babel.config.js file:

module.exports = {
  presets: ['module:metro-react-native-babel-preset'],
};

jest.config.js file:

module.exports = {
  preset: 'react-native',
  moduleFileExtensions: ['ts', 'tsx', 'js', 'jsx', 'json', 'node'],
}

Note: I am using react-native type-script template, like react-native init MyApp --template typescript

Answer

Brian Adams picture Brian Adams · Apr 23, 2019

Some react-native libraries ship uncompiled ES6 code.

ES6 code needs to be compiled before it can be run by Jest.

The Jest doc about Testing React Native Apps includes a section about compiling dependencies that don't ship pre-compiled code.

You will need to tell Jest to compile react-navigation-tabs by whitelisting it in the transformIgnorePatterns option in your Jest config.

Example:

Changing the jest.config.js file into something like below, fixed the issue mentioned in OP.

But the "react-native-reanimated" module (which requires native integration, as described in another post) needs further work, and we should Mock modules with such native requirements... 

module.exports = {
  preset: 'react-native',
  moduleFileExtensions: ['ts', 'tsx', 'js', 'jsx', 'json', 'node'],
  transformIgnorePatterns: [
    "node_modules/(?!(react-native"
      + "|react-navigation-tabs"
      + "|react-native-splash-screen"
      + "|react-native-screens"
      + "|react-native-reanimated"
    + ")/)",
  ],
}

Note: the transformIgnorePatterns option (which is an array of Regular-Expressions) is originally meant to exclude files from being compiled, but using (?!(some-dir-name|another-name)) pattern (the (?!...), negative look-ahead), we do tell Jest to exclude anything in node_modules directory, except the names that we did specify.

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