React Native - Jest: Broken since update to 0.56.

Question

Ever since upgrading to the new React Native version my tests are broken.

Environment

Here is my environment:

React Native Environment Info:
System:
  OS: macOS High Sierra 10.13.4
  CPU: x64 Intel(R) Core(TM) i7-7920HQ CPU @ 3.10GHz
  Memory: 486.81 MB / 16.00 GB

  Shell: 3.2.57 - /bin/bash
Binaries:
  Node: 9.4.0 - /usr/local/bin/node
  npm: 6.1.0 - /usr/local/bin/npm
  Watchman: 4.9.0 - /usr/local/bin/watchman
SDKs:
  iOS SDK:
    Platforms: iOS 11.4, macOS 10.13, tvOS 11.4, watchOS 4.3
IDEs:
  Android Studio: 3.1 AI-173.4697961
  Xcode: 9.4.1/9F2000 - /usr/bin/xcodebuild
npmPackages:
  react: 16.4.1 => 16.4.1
  react-native: 0.56.0 => 0.56.0
npmGlobalPackages:
  create-react-native-app: 1.0.0
  react-native-cli: 2.0.1
  react-native-git-upgrade: 0.2.7

Description

While trying to test my newly created action creators,npm test throws the following error:

jest

 FAIL  app/actions/logout/logout.test.js
  ● Test suite failed to run


    Plugin 0 specified in "/Users/jan/Startup/react-native/ordersome/node_modules/babel-preset-react-native/index.js" provided an invalid
property of "default" (While processing preset: "/Users/jan/Startup/react-native/ordersome/node_modules/babel-preset-react-native/index.js
")

      at Plugin.init (node_modules/babel-core/lib/transformation/plugin.js:131:13)
      at Function.normalisePlugin (node_modules/babel-core/lib/transformation/file/options/option-manager.js:152:12)
      at node_modules/babel-core/lib/transformation/file/options/option-manager.js:184:30
          at Array.map (<anonymous>)
      at Function.normalisePlugins (node_modules/babel-core/lib/transformation/file/options/option-manager.js:158:20)
      at OptionManager.mergeOptions (node_modules/babel-core/lib/transformation/file/options/option-manager.js:234:36)
      at node_modules/babel-core/lib/transformation/file/options/option-manager.js:265:14
      at node_modules/babel-core/lib/transformation/file/options/option-manager.js:323:22
          at Array.map (<anonymous>)
      at OptionManager.resolvePresets (node_modules/babel-core/lib/transformation/file/options/option-manager.js:275:20)

I have googled heavily and can't find a fix. It seems like it has something to do with babel.

Reproducible Demo

It's easy to reproduce (currently). I tried an started a new project using react-native init. Then I just created a random .test.js file and wrote the getting started test of the documentation in it:

function sum(a, b) {
  return a + b;
}

test("adds 1 + 2 to equal 3", () => {
  expect(sum(1, 2)).toBe(3);
});

Next I run 'npm test' and it gives the error above.

Answer 1

@J. Hesters solution is almost correct. But is not necesary to install babel, just adding the transform solves the issue.

{
  ...
  "jest": {
    "preset": "react-native",
    "transform": {
      "^.+\\.js$": "<rootDir>/node_modules/react-native/jest/preprocessor.js"
    }
  }
  ...
}

My previous response has some side effects that i did not see until after trying to rebuild the entire react-native application. So please dont use it.

PREVIOUS ANSWER

is actually nothing to do with react-native 0.56. is caused by the babel presets 5, just revert this package will do the trick.

yarn add babel-preset-react-native@4.0.0

Answer 2

Here is how I fixed it.

Add

"@babel/core": "^7.0.0-beta.47",
"babel-core": "^7.0.0-beta.47",

to your package.json and run npm install. This fixed it for me.

Furthermore for Enzyme you will have to add

   "transform": {
      "^.+\\.js$": "<rootDir>/node_modules/react-native/jest/preprocessor.js"
    }

to you jest config in your package.json.

If you want to see a more thorough fix, check out this github issue.

Answer 3

I had the same mistake, and also I added:

"transform": {
      "^.+\\.js$": "<rootDir>/node_modules/react-native/jest/preprocessor.js"
    }

But then I got another mistake in another module, and to ignore it you need to add this code to your setup.jest.js file:

jest.mock('react-native-router-flux', () => {
    return {
        Crashlytics: {
            crash: () => {},
        },
        Answers: {
            logCustom: () => {},
            logContentView: () => {},
        },
    }

So after this code jest will ignore error in "react-native-router-flux" module in your tests.

Answer 4

The problem is with 0.56.0.

The only solution is running it with v0.55.4

either install the v0.55.4 by: npm i --save react-native@0.55.4

or when running the app run by: react-native run-android --version 0.55.4

This helped me, hope it helps