Jest encountered an unexpected token + react markdown

Question

I'm getting an error when trying to run my test file (I'm using react typescript)

  ● 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:

    export {uriTransformer} from './lib/uri-transformer.js'
    ^^^^^^

    SyntaxError: Unexpected token 'export'

       5 | const Markdown = ({ text, classStyle }: ITextMedia) => (
       6 |   <div className={`${classes.mediaParagraph} ${classStyle ?? ''}`}>
    >  7 |     <ReactMarkdown>{text}</ReactMarkdown>
         |                                             ^
       8 |   </div>
       9 | );
      10 | export default Markdown;

      at Runtime.createScriptFromCode (node_modules/jest-runtime/build/index.js:1728:14)
      at Object.<anonymous> (components/media/markdown/index.tsx:7:45)

I already tried adding the React markdown to the transform ignore patterns, but it still doesn't work

here's my jest.config

{
  setupFilesAfterEnv: ['<rootDir>/jest.setup.js'],
  moduleDirectories: ['node_modules', '<rootDir>/'],
  testEnvironment: 'jest-environment-jsdom',
  moduleNameMapper: {
    'next/router': '<rootDir>/__mocks__/next/router.js',
    '^.+\\.module\\.(css|sass|scss)$': 'identity-obj-proxy',
    '^.+\\.(jpg|jpeg|png|gif|webp|avif|svg)$': '<rootDir>/__mocks__/file-mock.js',
  },
  transform: {
    '^.+\\.(js|jsx)$': 'babel-jest'
  },
  transformIgnorePatterns: [
    'node_modules/(?!react-markdown/)'
  ]
}

my babel config:

{
    "presets": [
        "next/babel",
        "@babel/preset-env"
    ],
    "plugins": []
}

I'm new to jest, so I'm not sure if I'm doing something wrong

Answer 1

In the jest.config file, you need to add the following to the moduleNameMapper attribute:

"react-markdown": "<rootDir>/node_modules/react-markdown/react-markdown.min.js"

So effectively, your moduleNameMapper should really look like this:

  ...
  moduleNameMapper: {
    'next/router': '<rootDir>/__mocks__/next/router.js',
    '^.+\\.module\\.(css|sass|scss)$': 'identity-obj-proxy',
    '^.+\\.(jpg|jpeg|png|gif|webp|avif|svg)$': '<rootDir>/__mocks__/file-mock.js',
    'react-markdown': '<rootDir>/node_modules/react-markdown/react-markdown.min.js',
  },
  ...

Good luck!