[ReactNative] Fix dimensions in jest tests

Libraries/BatchedBridge/BatchedBridgedModules/__mocks__/NativeModules.js

@@ -29,6 +29,7 @@ var NativeModules = {
   UIManager: {
     customBubblingEventTypes: {},
     customDirectEventTypes: {},
+    Dimensions: {},
   },
   AsyncLocalStorage: {
     getItem: jest.genMockFunction(),

Libraries/Utilities/Dimensions.js

@@ -20,7 +20,7 @@ var dimensions = NativeModules.UIManager.Dimensions;
 // We calculate the window dimensions in JS so that we don't encounter loss of
 // precision in transferring the dimensions (which could be non-integers) over
 // the bridge.
-if (dimensions.windowPhysicalPixels) {
+if (dimensions && dimensions.windowPhysicalPixels) {
   // parse/stringify => Clone hack
   dimensions = JSON.parse(JSON.stringify(dimensions));
 

Libraries/Utilities/__mocks__/ErrorUtils.js

@@ -0,0 +1,23 @@
+// This mock only provides short-circuited methods of applyWithGuard and guard.
+// A lot of modules rely on these two functions. This mock relieves their tests
+// from depending on the real ErrorUtils module. If you need real error handling
+// don't use this mock.
+'use strict';
+
+function execute(fun, context, args) {
+  return fun.apply(context, args);
+};
+
+function reportError(error) {
+  throw error;
+}
+
+var ErrorUtils = {
+  apply: jest.genMockFunction().mockImplementation(execute),
+  applyWithGuard: jest.genMockFunction().mockImplementation(execute),
+  inGuard: jest.genMockFunction().mockReturnValue(true),
+  reportError: jest.genMockFunction().mockImplementation(reportError),
+  setGlobalHandler: jest.genMockFunction(),
+};
+
+module.exports = ErrorUtils;

Libraries/Utilities/__mocks__/PixelRatio.js

@@ -0,0 +1,20 @@
+/**
+ * Copyright 2004-present Facebook. All Rights Reserved.
+ */
+'use strict';
+
+var PixelRatio = {
+  startDetecting: function () {
+    // noop for our implementation
+  },
+
+  get: function() {
+    return 2;
+  },
+
+  getPixelSizeForLayoutSize: function (layoutSize) {
+    return Math.round(layoutSize * PixelRatio.get());
+  }
+};
+
+module.exports = PixelRatio;