Jest encountered unexpected token with React app

🐛 Bug Report

When trying to run tests with Jest in a React app, I get a Jest encountered an unexpected token error. I copied the Link component and test directly from here. This is the error:

FAIL  src/components/Link.test.js
  ● 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:

    SyntaxError: C:\workspace\react\testapp\src\components\Link.test.js: Unexpected token (8:4)

       6 | test('Link changes the class when hovered', () => {
       7 |   const component = renderer.create(
    >  8 |     <Link page="http://www.facebook.com">Facebook</Link>,
         |     ^
       9 |   );
      10 |   let tree = component.toJSON();
      11 |   expect(tree).toMatchSnapshot();

      at Parser.raise (node_modules/@babel/parser/lib/index.js:3938:15)
      at Parser.unexpected (node_modules/@babel/parser/lib/index.js:5247:16)
      at Parser.parseExprAtom (node_modules/@babel/parser/lib/index.js:6327:20)
      at Parser.parseExprSubscripts (node_modules/@babel/parser/lib/index.js:5923:21)
      at Parser.parseMaybeUnary (node_modules/@babel/parser/lib/index.js:5902:21)
      at Parser.parseExprOps (node_modules/@babel/parser/lib/index.js:5811:21)
      at Parser.parseMaybeConditional (node_modules/@babel/parser/lib/index.js:5783:21)
      at Parser.parseMaybeAssign (node_modules/@babel/parser/lib/index.js:5730:21)
      at Parser.parseExprListItem (node_modules/@babel/parser/lib/index.js:6994:18)
      at Parser.parseCallExpressionArguments (node_modules/@babel/parser/lib/index.js:6123:22)

Here’s my package.json

{
  "name": "testapp",
  "version": "1.0.0",
  "main": "index.js",
  "license": "MIT",
  "scripts": {
    "start": "webpack-dev-server --config ./config/webpack.config.development.js",
    "build": "webpack -p --config ./config/webpack.config.production.js",
    "test": "jest"
  },
  "dependencies": {
    "axios": "^0.18.0",
    "moment": "^2.22.2",
    "polished": "^2.0.3",
    "prop-types": "^15.6.2",
    "react": "^16.4.2",
    "react-delay-render": "^0.1.2",
    "react-dom": "^16.4.2",
    "react-imported-component": "^4.6.2",
    "react-router-dom": "^4.3.1",
    "simple-grid": "^1.0.1",
    "styled-components": "^3.4.5",
    "uuid": "^3.3.2",
    "validator": "^10.7.0"
  },
  "devDependencies": {
    "@babel/core": "^7.0.0",
    "@babel/plugin-proposal-class-properties": "^7.0.0",
    "@babel/plugin-syntax-dynamic-import": "^7.0.0",
    "@babel/preset-env": "^7.0.0",
    "@babel/preset-react": "^7.0.0",
    "babel-core": "7.0.0-bridge.0",
    "babel-jest": "^23.4.2",
    "babel-loader": "^8.0.0",
    "babel-plugin-styled-components": "^1.6.0",
    "css-loader": "^1.0.0",
    "html-webpack-plugin": "^3.2.0",
    "jest": "^23.5.0",
    "mini-css-extract-plugin": "^0.4.2",
    "react-test-renderer": "^16.4.2",
    "regenerator-runtime": "^0.12.1",
    "style-loader": "^0.23.0",
    "webpack": "^4.17.1",
    "webpack-cli": "^3.1.0",
    "webpack-dev-server": "^3.1.7"
  }
}

Here’s my .babelrc file (located in the root directory):

{
  "plugins": [
    "@babel/plugin-proposal-class-properties",
    "babel-plugin-styled-components",
    "@babel/plugin-syntax-dynamic-import"
  ],
  "presets": ["@babel/preset-env", "@babel/preset-react"],
  "env": {
    "development": {
      "plugins": [
        "@babel/plugin-proposal-class-properties",
        ["babel-plugin-styled-components", { "displayName": true }],
        "@babel/plugin-syntax-dynamic-import"
      ],
      "presets": ["@babel/preset-env", "@babel/preset-react"]
    },
    "test": {
      "plugins": [
        "@babel/plugin-proposal-class-properties",
        ["babel-plugin-styled-components", { "displayName": true }],
        "@babel/plugin-syntax-dynamic-import"
      ],
      "presets": ["@babel/preset-env", "@babel/preset-react"]
    },
    "production": {
      "plugins": [
        "@babel/plugin-proposal-class-properties",
        "babel-plugin-styled-components",
        "@babel/plugin-syntax-dynamic-import"
      ],
      "presets": ["@babel/preset-env", "@babel/preset-react"]
    }
  }
}

To Reproduce

Steps to reproduce the behavior:

• Install Jest with yarn add --dev babel-jest babel-core@^7.0.0-0 @babel/core
• Create a test
• Run yarn test

Expected behavior

• Jest should work

Run npx envinfo --preset jest

Paste the results here:

OS: Windows 10
    CPU: x64 Intel(R) Xeon(R) CPU E3-1505M v6 @ 3.00GHz
  Binaries:
    Yarn: 1.5.1 - C:\Program Files (x86)\Yarn\bin\yarn.CMD
    npm: 5.6.0 - C:\Program Files\nodejs\npm.CMD

[hoaiduyit]

I have the same problem too.

[hoaiduyit]

After 3 days, I just find out the solutions for this issue. There are 2 solutions for this:

Solution 1:

You can change your file name from .babelrc to babel.config.js, and this will work.

Solution 2:

I’m using this way. Create a transform file like this (mine is jest-transforme.js):

const config = {
  babelrc: false,
  presets: [
    [
      "@babel/env",
      {
        modules: false
      }
    ],
    "@babel/react"
  ],
  plugins: [
    ["@babel/plugin-proposal-decorators", { legacy: true }],
    ["@babel/plugin-proposal-class-properties", { loose: true }],
    "transform-es2015-modules-commonjs"
  ]
};
module.exports = require("babel-jest").createTransformer(config);

Here’s my jest.config.js:

module.exports = {
  collectCoverageFrom: ["src/**/*.{js,jsx,mjs}"],
  testMatch: ["<rootDir>/src/**/__tests__/**/*.{js,jsx,mjs}", "<rootDir>/src/**/?(*.)(spec|test).{js,jsx,mjs}"],
  transform: {
    "^.+\\.(js|jsx|mjs)$": "<rootDir>/config/jest/jest-transformer.js"
  },
  transformIgnorePatterns: ["[/\\\\]node_modules[/\\\\].+\\.(js|jsx|mjs)$"]
};

And my I still have my .babelrc

const enviroments = require("./env-config.js");

module.exports = {
  presets: [
    [
      "next/babel",
      {
        "preset-env": {
          useBuiltIns: "entry"
        }
      }
    ]
  ],
  plugins: [
    ["styled-components", { ssr: true, displayName: true, preprocess: false }],
    [
      "module-resolver",
      {
        root: ["./"]
      }
    ]
  ],
  env: {
    dev: {
      plugins: [
        ["transform-define", enviroments],
        ["module-resolver", { root: ["./"] }],
        "transform-decorators-legacy",
        "transform-class-properties"
      ]
    },
    build: {
      plugins: [
        ["transform-define", enviroments],
        ["module-resolver", { root: ["./"] }],
        "transform-decorators-legacy",
        "transform-class-properties"
      ]
    },
    production: {
      presets: [
        [
          "minify", // why add minify here, we run uglify over the whole code bundles
          {
            mangle: false,
            evaluate: false
          }
        ]
      ],
      plugins: [
        ["transform-define", enviroments],
        ["@babel/plugin-proposal-decorators", { legacy: true }],
        ["@babel/plugin-proposal-class-properties", { loose: true }],
        ["module-resolver", { root: ["./"] }]
      ],
      comments: false,
      compact: true,
      minified: true
    }
  }
};

Hope this can have you guys pass this issue. Cheer.