Use jest to mock electron in tests

Summary:
Replacing our custom electron-stubs transform with a mocked module.

This will now be the default impl for tests, and we can override it by mocking as needed.

Reviewed By: passy

Differential Revision: D17979659

fbshipit-source-id: a26994158d439fa7dc1ca38225294106fc4e1559

__mocks__/electron.tsx

@@ -0,0 +1,23 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ */
+
+module.exports = {
+  remote: {
+    process: {
+      env: {},
+    },
+    app: {
+      getAppPath: process.cwd,
+      getVersion: () => '0.9.99',
+      relaunch: () => {},
+      exit: () => {},
+    },
+    getCurrentWindow: () => ({isFocused: () => true}),
+  },
+};

src/__tests__/server.device.tsx

@@ -7,6 +7,13 @@
  * @format
  */
 
+jest.mock('../fb-stubs/Logger');
+try {
+  jest.mock('../fb/Logger');
+} catch {
+  // Allowed to fail when fb modules are not present.
+}
+
 import Server from '../server';
 import {init as initLogger} from '../fb-stubs/Logger';
 import reducers, {Store} from '../reducers/index';

static/transforms/index.js

@@ -63,12 +63,8 @@ function transform({filename, options, src}) {
 
   if (process.env.BUILD_HEADLESS) {
     plugins.push(require('./electron-stubs.js'));
-    plugins.push(require('./electron-requires.js'));
-  } else if (options.isTestRunner) {
-    if (process.env.USE_ELECTRON_STUBS) {
-      plugins.push(require('./electron-stubs.js'));
   }
-  } else {
+  if (!options.isTestRunner) {
     // Replacing require statements with electronRequire to prevent metro from
     // resolving them. electronRequire are resolved during runtime by electron.
     // As the tests are not bundled by metro and run in @jest-runner/electron,