Jest error Unexpected token ... (ES6)

Question

I am getting the following error whenever I run jest in commandline:

 ● Test suite failed to run

/Users/<USER>/<Project>/src/login/LoginAPI.js:13
        ...headers,
        ^^^

SyntaxError: Unexpected token ...

The code that it breaks on uses ES6 ellipses:

headers: {
    ...headers
},

This is what my .babelrc file looks like:

{ "presets":["env", "react"] }

And this is what I have in my package.json:

"dependencies": {
    "express": "^4.15.4",
    "express-healthcheck": "^0.1.0",
    "js-cookie": "^2.1.4",
    "normalize.css": "^7.0.0",
    "query-string": "^5.0.0",
    "react": "^15.6.1",
    "react-dom": "^15.6.1",
    "react-router-dom": "^4.2.2"
  },
  "devDependencies": {
    "babel-jest": "^21.2.0",
    "babel-preset-env": "^1.6.1",
    "babel-preset-es2015": "^6.24.1",
    "enzyme": "^3.1.0",
    "enzyme-adapter-react-15": "^1.0.2",
    "jest": "^21.2.1",
    "jest-cli": "^21.2.1",
    "react-scripts": "1.0.10"
  },
  "jest": {
    "moduleNameMapper": {
      "\\.(jpg|jpeg|png|gif|eot|otf|webp|svg|ttf|woff|woff2|mp4|webm|wav|mp3|m4a|aac|oga)$": "<rootDir>/__mocks__/fileMock.js",
      "\\.(css|less)$": "<rootDir>/__mocks__/styleMock.js"
    },
    "moduleFileExtensions": ["js"],
    "moduleDirectories": [
      "node_modules",
      "bower_components",
      "shared"
    ],
    "testPathIgnorePatterns": [
      "/node_modules/",
      "/yarn-cache/"
    ]
  }

Answer 1

You need to use a specific babel preset for this syntax. Check this preset

npm install --save-dev babel-plugin-transform-object-rest-spread

And then add this to your .babelrc

{
  "plugins": ["transform-object-rest-spread"]
}

You might want to add stage-2 as it has more ES6 goodies.

Note: Jest can read your .babelrc file

Answer 2

In babel 7, babel-plugin-transform-object-rest-spread will report error: SpreadProperty has been renamed to SpreadElement.

So I use:

npm install --save-dev @babel/plugin-proposal-object-rest-spread

and config .babelrc

{
  "plugins": ["@babel/plugin-proposal-object-rest-spread"]
}