Test platform specific extension code for React Native

Question

Currently, React Native dynamically requires a file for the running platform with an specific file extension, *.ios.js or *.android.js. However, when running this code inside a test environment, we get a require error because the module require('./module') cannot be found in the file tree, which looks like:

• module.ios.js
• module.android.js

How can we handle this issues in a test environment?

Answer 1

Adding platform specific extensions to moduleFileExtensions fixed the problem for me with jest.14.1. Credits to : github link

Here is a snippet from sample package.json which will run all files including scene.jest.js(x).

...
"jest": {
    "verbose": true,
    "preset": "jest-react-native",
    "moduleFileExtensions": ["js", "android.js", "ios.js"],
    "testRegex": "\\.scene\\.jest\\.jsx$"
  }
 ...

Answer 2

As of Jest 17.0.0 you can use the defaultPlatform configuration for this - see the very bottom of the Jest React Native tutorial.

As it shows there, you would configure something like this:

"haste": {
  "defaultPlatform": "ios",
  "platforms": ["android", "ios"],
},

Naturally, this will mean your tests only load the iOS version of your component (or only Android, depending how you choose to configure it).

If you find it important to test both versions, you'll probably need to do something more like the solution mentioned in this issue, possibly manipulating Platform.OS and using require.requireActual directly.

(Might also want to track this issue, in case a less hacky solution is eventually found.)