chore(desktop): add Vitest + testing-library

Install Vitest, @testing-library/react, jest-dom, jsdom. Add test + test:watch scripts. Mirrors ui/web vitest config.

ui/desktop/frontend/package.json

@@ -6,7 +6,9 @@
   "scripts": {
     "dev": "vite",
     "build": "tsc -b && vite build",
-    "preview": "vite preview"
+    "preview": "vite preview",
+    "test": "vitest run",
+    "test:watch": "vitest"
   },
   "dependencies": {
     "@dnd-kit/core": "^6.3.1",
@@ -30,12 +32,16 @@
   },
   "devDependencies": {
     "@tailwindcss/vite": "^4.2.2",
+    "@testing-library/jest-dom": "^6.9.1",
+    "@testing-library/react": "^16.3.2",
     "@types/react": "^19.2.14",
     "@types/react-dom": "^19.2.3",
     "@types/react-syntax-highlighter": "^15.5.13",
     "@vitejs/plugin-react": "^6.0.1",
+    "jsdom": "^29.0.2",
     "tailwindcss": "^4.2.2",
     "typescript": "^6.0.2",
-    "vite": "^8.0.8"
+    "vite": "^8.0.8",
+    "vitest": "^4.1.4"
   }
 }

ui/desktop/frontend/src/test/setup.ts

@@ -0,0 +1,15 @@
+import '@testing-library/jest-dom'
+
+// Mock HTMLMediaElement — jsdom doesn't implement audio playback
+Object.defineProperty(window.HTMLMediaElement.prototype, 'play', {
+  configurable: true,
+  value: () => Promise.resolve(),
+})
+Object.defineProperty(window.HTMLMediaElement.prototype, 'pause', {
+  configurable: true,
+  value: () => undefined,
+})
+Object.defineProperty(window.HTMLMediaElement.prototype, 'load', {
+  configurable: true,
+  value: () => undefined,
+})

ui/desktop/frontend/src/test/smoke.test.ts

@@ -0,0 +1,7 @@
+import { describe, it, expect } from 'vitest'
+
+describe('vitest sanity', () => {
+  it('boots', () => {
+    expect(true).toBe(true)
+  })
+})

ui/desktop/frontend/vitest.config.ts

@@ -0,0 +1,15 @@
+import { defineConfig } from 'vitest/config'
+import path from 'path'
+
+export default defineConfig({
+  test: {
+    environment: 'jsdom',
+    globals: true,
+    setupFiles: ['./src/test/setup.ts'],
+  },
+  resolve: {
+    alias: {
+      '@': path.resolve(__dirname, './src'),
+    },
+  },
+})