Tests fail in a react-native-web app with __DEV__ is not defined

[tlvince]

In a fresh app created by create-react-app using React Native for Web, running src/root/Root.test.js throws ReferenceError: __DEV__ is not defined.

I would assume an equivalent of #407 (aliasing react-native to react-native-web) is necessary in the test environment. If I temporarily manually symlink react-native-web to react-native in node_modules and re-run the tests, they pass as expected.

Expected behavior

Tests to pass.

Actual behaviour

 FAIL  src/root/Root.test.js
  ● Test suite failed to run

    ReferenceError: __DEV__ is not defined
      
      at Object.<anonymous> (node_modules/react-native/Libraries/react-native/react-native.js:15:5)
      at Object.<anonymous> (src/app/App.js:3:18)
      at Object.<anonymous> (src/root/Root.js:3:10)
      at Object.<anonymous> (src/root/Root.test.js:5:11)
      at process._tickCallback (internal/process/next_tick.js:103:7)

Environment

Run these commands in the project folder and fill in their results:

1. npm ls react-scripts (if you haven’t ejected): 0.7.0
2. node -v: 6.9.1
3. npm -v: 3.10.9

Then, specify:

1. Operating system: OS X 10.10.5
2. Browser and version: Chrome v53

[gaearon]

This is probably fixable using moduleNameMapper as described here.
Something like

    "moduleNameMapper": {
      "^react-native$": "react-native-web",
    }

If this works, would you like to send a PR?

[ross-rosario]

I've just stumbled that issue with similar circumstances; running tests in a CRA app while RNW is in use. @gaearon's suggestion works perfectly. Here is a pull request that includes the change #1201.