Jest Mocks for NetInfo and Linking

Summary:
This isn't exhaustive, but it's a few more functions that these modules normally export which need to be stubbed.
Closes https://github.com/facebook/react-native/pull/14432

Differential Revision: D5345928

Pulled By: shergin

fbshipit-source-id: f333056ac43ce7c75c6734bca8dc9035745721df

jest/setup.js

@@ -143,6 +143,11 @@ const mockNativeModules = {
     canOpenURL: jest.fn(
       () => new Promise((resolve) => resolve(true))
     ),
+    addEventListener: jest.fn(),
+    getInitialURL: jest.fn(
+      () => new Promise((resolve) => resolve())
+    ),
+    removeEventListener: jest.fn(),
   },
   LocationObserver: {
     getCurrentPosition: jest.fn(),
@@ -150,6 +155,18 @@ const mockNativeModules = {
     stopObserving: jest.fn(),
   },
   ModalFullscreenViewManager: {},
+  NetInfo: {
+    fetch: jest.fn(
+      () => new Promise((resolve) => resolve())
+    ),
+    addEventListener: jest.fn(),
+    isConnected: {
+      fetch: jest.fn(
+        () => new Promise((resolve) => resolve())
+      ),
+      addEventListener: jest.fn(),
+    },
+  },
   Networking: {
     sendRequest: jest.fn(),
     abortRequest: jest.fn(),