[Regression] Jest no longer works out of the box

[deecewan]

• Review the documentation: https://facebook.github.io/react-native
• Search for existing issues: https://github.com/facebook/react-native/issues
• Use the latest React Native release: https://github.com/facebook/react-native/releases

Environment

  React Native Environment Info:
    System:
      OS: macOS High Sierra 10.13.1
      CPU: x64 Intel(R) Core(TM) i7-6700HQ CPU @ 2.60GHz
      Memory: 69.45 MB / 16.00 GB
      Shell: 5.4.2 - /usr/local/bin/zsh
    Binaries:
      Node: 8.11.1 - ~/.nvm/versions/node/v8.11.1/bin/node
      Yarn: 1.9.2 - /usr/local/bin/yarn
      npm: 5.6.0 - ~/.nvm/versions/node/v8.11.1/bin/npm
      Watchman: 4.9.0 - /usr/local/bin/watchman
    SDKs:
      iOS SDK:
        Platforms: iOS 11.2, macOS 10.13, tvOS 11.2, watchOS 4.2
      Android SDK:
        Build Tools: 23.0.1, 23.0.3, 25.0.1, 25.0.3, 26.0.1, 26.0.2, 27.0.3
        API Levels: 23, 25, 26, 27
    IDEs:
      Android Studio: 3.1 AI-173.4720617
      Xcode: 9.2/9C40b - /usr/bin/xcodebuild
    npmPackages:
      react: 16.4.1 => 16.4.1
      react-native: 0.56.0 => 0.56.0

Description

After upgrading to React Native v0.56.0, jest no longer works.
It is missing a babel-core bridge and the @babel/core dependency.
Once these are added, previously working tests no longer work if the source contains code that requires transpilation.

To confirm, my tests ran fine under v0.55.4 - after the upgrade, they started to fail. I was able to reproduce a minimal demo using react-native init

Reproducible Demo

Edit: I've created a repo that has the project set up the exact same with 0.55.4 and 0.56.0.

• run react-native init <any name>
• add a dependency on react-native-vector-icons (the same issue also happens with react-native-pie-chart, but only one is required)
  • yarn add react-native-vector-icons && yarn react-native link react-native-vector-icons
• in App.js, add import Icon from 'react-native-vector-icons/MaterialIcons';
• echo "import App from './App';" > App.test.js
  • You technically need to have at least one test in this file, but it will never get past the parse stage.
• yarn test

This will result in an error due to incorrect babel versions:

This one is pretty easily resolved with yarn add -D babel-core@7.0.0-bridge.0.

Running the yarn test again will result in the following errors:

[deecewan]

I've just created a repo to demonstrate this regression. Doing the exact same steps as I've listed above (short of upgrading the babel-core version) in 0.55.4 results in a successful test.

[ferdicus]

duplicate? #19859

[hramos]

Duplicate of #19859