Improve and document jest mock setup (#651)

Author: wcandillon

docs/docs/getting-started/installation.md

@@ -53,4 +53,23 @@ cd package && yarn && cd ..
 cd example && yarn && yarn start
 ```
 
-To run the example project on iOS, you will need to run `pod install`, and on Android, you will also need Android NDK to be installed ([see here](#android)).
+To run the example project on iOS, you will need to run `pod install`, and on Android, you will also need Android NDK to be installed ([see here](#android)). 
+
+## Testing with Jest
+
+In order to load the mock provided by React Native Skia add following to your jest config:
+
+```json
+"setupFiles": ["./node_modules/@shopify/react-native-skia/jestSetup.js"]
+```
+
+Example:
+
+```json
+"jest": {
+  "preset": "react-native",
+  "setupFiles": ["./node_modules/@shopify/react-native-skia/jestSetup.js"]
+}
+```
+
+

package/jestSetup.js

@@ -0,0 +1,4 @@
+/* globals jest */
+jest.mock("@shopify/react-native-skia", () =>
+  require("@shopify/react-native-skia/lib/commonjs/mock")
+);

package/package.json

@@ -21,6 +21,7 @@
     "android/src/**",
     "libs/android/**",
     "index.js",
+    "jestSetup.js",
     "cpp/**/*.{h,cpp}",
     "ios",
     "libs/ios/libskia.xcframework",