Generating new Jest Mocks

This document will guide you through the process of generating new Jest Mocks for packages/jest-expo module using apps/jest-expo-mock-generator.

Why

We provide some mocks of our native methods which are generated by traversing all the modules and its methods and making a configuration of all those methods with the number of arguments etc.

How

1. In your terminal, go to apps/jest-expo-mock-generator

• run yarn to ensure the dependencies are installed
• run expo start to start the Expo server

2. Open the Expo Go project on iOS by opening ios/Exponent.xcworkspace

• run the project on a simulator or a device

3. Open jest-expo-mock-generator in the running Expo Go app

4. After the app is finished opening, in the terminal, where the Expo server is running, you should see a big chunk of text wrapped with

   ------------------------------COPY THE TEXT BELOW------------------------------

   and

   ------------------------------END OF TEXT TO COPY------------------------------

   lines. Select and copy the text from between those lines.

https://user-images.githubusercontent.com/379606/120577838-b4964a80-c3d9-11eb-93db-aba3ea9eef41.mp4

5. Stop the Expo server running in apps/jest-expo-mock-generator, started in step 1.

6. Paste the copied text into packages/jest-expo/src/preset/expoModules.js.

7. In the terminal, go into packages/jest-expo.

8. Run yarn prettier src/preset/expoModules.js --write.

9. Commit the changes. Bonus points for not modifying mock values (like deviceYearClass), which will be different if you use a test device different than the one used before.