Fix test fail

- Fixed unit test failure after the change of using Electron's
`app.whenReady` API.
- Implemented unit test for function `createWindow`.
- Removed `mainWindow` from `main` export as its' value will
always be `undefined` the way it's exported.

Author: iamWing

src/main/main.ts

@@ -36,7 +36,7 @@ function createWindow() {
 // initialization and is ready to create browser windows.
 // Some APIs can only be used after this event occurs.
 app.whenReady().then(() => {
-  createWindow();
+  if (nodeEnv.dev || nodeEnv.prod) createWindow();
 
   app.on('activate', () => {
     if (BrowserWindow.getAllWindows.length === 0) createWindow();
@@ -59,5 +59,4 @@ ipcMain.on('renderer-ready', () => {
 // code. You can also put them in separate files and require them here.
 
 // eslint-disable-next-line import/prefer-default-export
-export const exportedForTests = nodeEnv.test
-  ? { mainWindow, createWindow } : undefined;
+export const exportedForTests = nodeEnv.test ? { createWindow } : undefined;

tests/main/main.spec.ts

@@ -1,10 +1,25 @@
 import { exportedForTests } from '_main/main';
+import { BrowserWindow } from 'electron';
 
 jest.mock('electron', () => ({
-  app: { on: jest.fn() },
+  app: {
+    on: jest.fn(),
+    whenReady: jest.fn(() => Promise.resolve()),
+  },
   ipcMain: { on: jest.fn() },
+  BrowserWindow: jest.fn().mockImplementation(() => ({
+    loadFile: jest.fn(() => Promise.resolve()),
+    on: jest.fn(),
+  })),
 }));
 
 test('Private props exported for unit tests', () => {
   expect(exportedForTests).toBeDefined();
 });
+
+test('func createWindow()', () => {
+  const { createWindow } = exportedForTests!;
+
+  createWindow();
+  expect(BrowserWindow).toHaveBeenCalledTimes(1);
+});