获取 Babel 将配置文件转换为 CommonJS

Question

I have a Nuxt app that I want to test with Jest and I can't get it to work. I have a setupFilesAfterEnv property set with a setupTests.ts that imports a translation file. This translations files uses ES6 import/export module syntax but it seems like my current configuration doesn't work to transpile it.

Isn't babel-jest supposed to transpile the .js files thanks to the transform property?

setupTests.ts

import { config } from '@vue/test-utils';
import flat from 'flat';
import '@testing-library/jest-dom/extend-expect';
import 'jest-axe/extend-expect';
import frenchTranslations from '~/config/translations/fr-FR';
...

babel.config.json

{
  "presets": ["@babel/preset-env", { "targets": { "node": "current" } }]
}

jest.config.js

module.exports = {
  moduleNameMapper: {
    '^@/(.*)$': '<rootDir>/$1',
    '^~/(.*)$': '<rootDir>/$1',
    '^vue$': 'vue/dist/vue.common.js',
  },
  moduleFileExtensions: ['ts', 'js', 'vue', 'json'],
  resolver: '<rootDir>/test/integration/resolver.js',
  transform: {
    '^.+\\.ts$': 'ts-jest',
    '^.+\\.js$': 'babel-jest',
    '^.+\\.vue$': '@vue/vue2-jest',
  },
  collectCoverage: true,
  collectCoverageFrom: [
    '<rootDir>/components/**/*.vue',
    '<rootDir>/pages/**/*.vue',
  ],
  testEnvironment: 'jsdom',
  passWithNoTests: true,
  setupFilesAfterEnv: ['<rootDir>/test/integration/setupTests.ts'],
};

/config/translations/fr-FR.js

export default {
 ...
}

Jest output

FAIL  test/integration/components/ui/RegistrationForm.test.ts
  ● 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:

    /my-project/config/translations/fr-FR.js:1
    ({"Object.<anonymous>":function(module,exports,require,__dirname,__filename,jest){export default {
                                                                                      ^^^^^^

    SyntaxError: Unexpected token 'export'

      1 | import { config } from '@vue/test-utils';
      2 | import flat from 'flat';
      3 | import '@testing-library/jest-dom/extend-expect';
      4 | import 'jest-axe/extend-expect';
    > 5 | import frenchTranslations from '~/config/translations/fr-FR';

      at Runtime.createScriptFromCode (node_modules/.pnpm/jest-runtime@28.1.1/node_modules/jest-runtime/build/index.js:1796:14)
      at Object.<anonymous> (test/integration/setupTests.ts:5:1)
      at TestScheduler.scheduleTests (node_modules/.pnpm/@jest+core@28.1.1/node_modules/@jest/core/build/TestScheduler.js:317:13)

----------------------|---------|----------|---------|---------|-------------------
File                  | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s
----------------------|---------|----------|---------|---------|-------------------
All files             |       0 |        0 |       0 |       0 |
 RegistrationForm.vue |       0 |        0 |       0 |       0 | 1-113
----------------------|---------|----------|---------|---------|-------------------
Test Suites: 1 failed, 1 total
Tests:       0 total
Snapshots:   0 total
Time:        1.35 s
Ran all test suites related to changed files.

Answer 1

Try changing your setupFilesAfterEnv to setupFilesAfterEnv: ['@testing-library/jest-dom/extend-expect'], and install dependency if necessary.

You may also want to try changing your babel.config.js file to:

// Need to convert modules to commonjs format so Jest can undertstand them.
const isTest = String(process.env.NODE_ENV) === 'test'
const isProd = String(process.env.NODE_ENV) === 'production'

module.exports = {
    // For transformation of TSX and other react related bable plugins
    presets: [
        // Allows smart transpilation according to target environments
        ['@babel/preset-env', { modules: isTest ? 'commonjs' : false }],
        // Enabling Babel to understand TypeScript
        '@babel/preset-typescript',
    ],
}

Note: disregard the typescript preset if your codebase is not in typescript.

Note2: Changing babel.config.json to babel.config.js may help as well.