Handle updater download failures for retry UI

Co-authored-by: MasterAcnolo <68693319+MasterAcnolo@users.noreply.github.com>

test/unit/autoUpdater.test.js

@@ -0,0 +1,53 @@
+const mockDownloadUpdate = jest.fn();
+const mockCheckForUpdates = jest.fn();
+const mockOn = jest.fn();
+const mockQuitAndInstall = jest.fn();
+
+jest.mock("electron-updater", () => ({
+  autoUpdater: {
+    autoDownload: true,
+    autoInstallOnAppQuit: true,
+    on: mockOn,
+    checkForUpdates: mockCheckForUpdates,
+    downloadUpdate: mockDownloadUpdate,
+    quitAndInstall: mockQuitAndInstall,
+  },
+}));
+
+jest.mock("electron", () => ({
+  app: {
+    isPackaged: true,
+  },
+}));
+
+const mockLoggerError = jest.fn();
+jest.mock("../../server/logger", () => ({
+  logger: {
+    info: jest.fn(),
+    warn: jest.fn(),
+    error: mockLoggerError,
+  },
+}));
+
+const { downloadUpdate } = require("../../app/autoUpdater");
+
+describe("autoUpdater.downloadUpdate", () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
+  test("resolves when electron-updater download succeeds", async () => {
+    mockDownloadUpdate.mockResolvedValue(undefined);
+
+    await expect(downloadUpdate()).resolves.toBeUndefined();
+    expect(mockDownloadUpdate).toHaveBeenCalledTimes(1);
+  });
+
+  test("rejects when electron-updater download fails", async () => {
+    const error = new Error("network down");
+    mockDownloadUpdate.mockRejectedValue(error);
+
+    await expect(downloadUpdate()).rejects.toThrow("network down");
+    expect(mockLoggerError).toHaveBeenCalledWith("Download failed:", "network down");
+  });
+});