/desktop-testing-electron

name: desktop-testing-electron
description: E2E testing with Playwright, main process unit testing, IPC testing, dialog/menu mocking, CI headless setup

Electron Testing Patterns

> **Quick Guide:** Use Playwright's `_electron.launch()` for E2E tests -- it controls the full app via CDP. Unit test main process code (IPC handlers, business logic) with your test runner by mocking the `electron` module. Test preload scripts by mocking `contextBridge` and `ipcRenderer`. Spectron is dead since Electron 24 -- Playwright and WebDriverIO are the replacements. Run Electron tests on headless Linux CI with `xvfb-run` or the `xvfb-maybe` wrapper.

---

<critical_requirements>

CRITICAL: Before Using This Skill

**(You MUST `await electronApp.close()` in test teardown -- leaked Electron processes break CI and consume resources)**

**(You MUST mock the `electron` module in unit tests -- Electron APIs are only available inside the Electron runtime)**

**(You MUST use `xvfb-run` or `xvfb-maybe` for headless Linux CI -- Electron requires a display server)**

**(You MUST stub native dialogs in E2E tests -- `showOpenDialog`/`showSaveDialog` block the process and cannot be interacted with by Playwright)**

</critical_requirements>

---

**Auto-detection:** Electron testing, \_electron.launch, electronApp, electronApplication, firstWindow, Playwright Electron, electron-mock-ipc, electron-playwright-helpers, stubDialog, xvfb, xvfb-run, xvfb-maybe, Spectron migration, ipcMain.handle test, ipcRenderer mock, contextBridge mock, BrowserWindow mock, Electron E2E, Electron unit test

**When to use:**

• Writing E2E tests for an Electron application with Playwright
• Unit testing main process code (IPC handlers, lifecycle logic)
• Mocking Electron modules (`dialog`, `BrowserWindow`, `ipcMain`, `ipcRenderer`)
• Testing preload scripts and `contextBridge` APIs
• Setting up headless CI for Electron tests (Linux xvfb)
• Migrating from Spectron to Playwright
• Screenshot/visual regression testing of Electron windows
• Testing auto-update flows

**When NOT to use:**

• Testing renderer UI in isolation (use your web testing skill -- renderer is standard web)
• Writing tests unrelated to Electron-specific APIs
• Performance profiling or benchmarking Electron apps
• Packaging or distributing Electron apps (use the Electron framework skill)

**Key patterns covered:**

• Playwright E2E: `_electron.launch()`, `firstWindow()`, `evaluate()`, assertions
• Main process unit testing with mocked Electron modules
• IPC handler testing (`ipcMain.handle` / `ipcRenderer.invoke`)
• Preload script testing (mock `contextBridge.exposeInMainWorld`)
• Dialog and menu stubbing in E2E tests
• Auto-updater test strategies
• Headless CI configuration (xvfb, GitHub Actions)
• Screenshot and visual regression testing
• Spectron migration path

---

<philosophy>

Philosophy

Electron testing splits along the same boundaries as the Electron process model:

1. **E2E tests** launch the full application with Playwright and exercise the complete flow -- main process, preload, renderer, and IPC together. These are slow but high-confidence. 2. **Main process unit tests** mock the `electron` module and test IPC handlers, lifecycle logic, and business logic in isolation. These are fast and catch logic bugs early. 3. **Renderer tests** are standard web tests -- the renderer is Chromium. Use your existing web testing approach.

**Guiding principle:** Test main process logic with unit tests, test integration through IPC with E2E, and test renderer UI with standard web tools. Don't try to unit test IPC communication itself -- the framework handles message passing. Test that your handlers produce the correct results given inputs.

**When to use E2E (Playwright):**

• Full user workflows (open file, edit, save)
• IPC round-trips that span main and renderer
• Window management (multi-window, modals, frameless)
• Visual regression / screenshot comparison
• Auto-update UI flow

**When to use unit tests:**

• IPC handler logic (validate input, produce output)
• Main process business logic (file operations, data processing)
• Preload API shape (correct channels exposed)
• Configuration and startup logic

</philosophy>

---

<patterns>

Core Patterns

Pattern 1: Playwright E2E -- Launch and Basic Assertions

Launch the Electron app, get the first window, and run assertions. Always close in teardown.

import { test, expect, _electron as electron } from "@playwright/test";
import type { ElectronApplication, Page } from "@playwright/test";

let electronApp: ElectronApplication;
let window: Page;

test.beforeEach(async () => {
  electronApp = await electron.launch({ args: ["dist/main.js"] });
  window = await electronApp.firstWindow();
});

test.afterEach(async () => {
  await electronApp.close();
});

test("shows main window with title", async () => {
  const title = await window.title();
  expect(title).toBe("My App");
  await expect(window.locator("h1")).toHaveText("Welcome");
});

**Why good:** `afterEach` guarantees cleanup, `firstWindow()` waits for the window to load, standard Playwright assertions work on the Page object

See [examples/core.md](examples/core.md) for evaluate(), multi-window, and environment variable patterns.

---

Pattern 2: Main Process Evaluation

Use `electronApp.evaluate()` to execute code in the main process context and access Electron APIs.

test("returns correct app version", async () => {
  const version = await electronApp.evaluate(async ({ app }) => {
    return app.getVersion();
  });
  expect(version).toMatch(/^\d+\.\d+\.\d+$/);
});

test("app path is set correctly", async () => {
  const appPath = await electronApp.evaluate(async ({ app }) => {
    return app.getAppPath();
  });
  expect(appPath).toContain("dist");
});

**Why good:** `evaluate()` receives the Electron `module` object (containing `app`, `BrowserWindow`, etc.) as its first argument, runs in the real main proces