[MM-40406] Add more singletons, refactor main.ts into pieces, add tests and some cleanup + tests for additional coverage (#1890)

* Refactor main.ts dependencies into singleton pattern

* Split main.ts into testable pieces, some other refactoring for singleton pattern

* Unit tests for main/app/app

* Unit tests for main/app/config

* Unit tests for main/app/initialize

* Unit tests for main/app/intercom

* Unit tests for main/app/utils

* Add some more tests to get to 70% coverage

* Fix for linux

* Fix for alternate data dir paths

* Fix E2E test

src/main/app/config.test.js

@@ -0,0 +1,108 @@
+// Copyright (c) 2016-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+import {app} from 'electron';
+
+import {RELOAD_CONFIGURATION} from 'common/communication';
+import Config from 'common/config';
+
+import {handleConfigUpdate} from 'main/app/config';
+import {handleNewServerModal} from 'main/app/intercom';
+import WindowManager from 'main/windows/windowManager';
+import AutoLauncher from 'main/AutoLauncher';
+
+jest.mock('electron', () => ({
+    app: {
+        isReady: jest.fn(),
+        setPath: jest.fn(),
+    },
+    ipcMain: {
+        emit: jest.fn(),
+        on: jest.fn(),
+    },
+}));
+jest.mock('electron-log', () => ({
+    info: jest.fn(),
+    error: jest.fn(),
+}));
+
+jest.mock('main/app/utils', () => ({
+    handleUpdateMenuEvent: jest.fn(),
+    updateSpellCheckerLocales: jest.fn(),
+    updateServerInfos: jest.fn(),
+}));
+jest.mock('main/app/intercom', () => ({
+    handleNewServerModal: jest.fn(),
+}));
+jest.mock('main/AutoLauncher', () => ({
+    enable: jest.fn(),
+    disable: jest.fn(),
+}));
+jest.mock('main/badge', () => ({
+    setUnreadBadgeSetting: jest.fn(),
+}));
+jest.mock('main/tray/tray', () => ({}));
+jest.mock('main/windows/windowManager', () => ({
+    handleUpdateConfig: jest.fn(),
+    sendToRenderer: jest.fn(),
+    initializeCurrentServerName: jest.fn(),
+}));
+
+describe('main/app/config', () => {
+    describe('handleConfigUpdate', () => {
+        beforeEach(() => {
+            AutoLauncher.enable.mockResolvedValue({});
+            AutoLauncher.disable.mockResolvedValue({});
+        });
+
+        afterEach(() => {
+            delete Config.registryConfigData;
+        });
+
+        it('should reload renderer config only when app is ready', () => {
+            handleConfigUpdate({});
+            expect(WindowManager.sendToRenderer).not.toBeCalled();
+
+            app.isReady.mockReturnValue(true);
+            handleConfigUpdate({});
+            expect(WindowManager.sendToRenderer).toBeCalledWith(RELOAD_CONFIGURATION);
+        });
+
+        it('should set download path if applicable', () => {
+            handleConfigUpdate({downloadLocation: '/a/download/location'});
+            expect(app.setPath).toHaveBeenCalledWith('downloads', '/a/download/location');
+        });
+
+        it('should enable/disable auto launch on windows/linux', () => {
+            const originalPlatform = process.platform;
+            Object.defineProperty(process, 'platform', {
+                value: 'win32',
+            });
+
+            handleConfigUpdate({});
+            expect(AutoLauncher.disable).toHaveBeenCalled();
+
+            handleConfigUpdate({autostart: true});
+            expect(AutoLauncher.enable).toHaveBeenCalled();
+
+            Object.defineProperty(process, 'platform', {
+                value: originalPlatform,
+            });
+        });
+
+        it('should recheck teams after config update if registry data is pulled in', () => {
+            const originalPlatform = process.platform;
+            Object.defineProperty(process, 'platform', {
+                value: 'win32',
+            });
+            Config.registryConfigData = {};
+
+            handleConfigUpdate({teams: []});
+            expect(handleNewServerModal).toHaveBeenCalled();
+
+            Object.defineProperty(process, 'platform', {
+                value: originalPlatform,
+            });
+        });
+    });
+});