test: fix Vitest runner, all 13 tests passing, add tests to CI

Vitest config fixes:
- Switch from jsdom to happy-dom (jsdom 28 has ESM compat issue
  with html-encoding-sniffer requiring @exodus/bytes)
- Add process.env.NODE_ENV='test' define so React exposes act()
  and testing utilities instead of production build

CI pipeline:
- Add 'bun run test' step to test-frontend job in ci.yml
- Tests now run on every PR alongside build and tsc checks

Test results: 3 suites, 13 tests, all passing in 713ms
- ErrorBoundary: renders children, shows fallback on error, shows buttons
- useGraphData: null handling, orphan filtering, edges, node attrs, layout
- useDirectoryMatrix: null handling, dir grouping, cross-dir deps, cycles

Closes OPE-10

Author: DevanshuNEU

.github/workflows/ci.yml

@@ -93,6 +93,10 @@ jobs:
       working-directory: ./frontend
       run: bun run build
 
+    - name: Run tests
+      working-directory: ./frontend
+      run: bun run test
+    
     - name: Check TypeScript
       working-directory: ./frontend
       run: bun run tsc --noEmit

frontend/bun.lock

@@ -58,7 +58,7 @@
     "@types/react-dom": "^18.2.17",
     "@vitejs/plugin-react": "^4.7.0",
     "autoprefixer": "^10.4.16",
-    "jsdom": "^28.1.0",
+    "happy-dom": "^20.7.0",
     "postcss": "^8.4.32",
     "tailwindcss": "^3.4.0",
     "typescript": "^5.9.3",

frontend/package.json

@@ -5,9 +5,13 @@ import path from 'path'
 
 export default defineConfig({
   plugins: [react()],
+  // force development mode so React exposes act() and test utilities
+  define: {
+    'process.env.NODE_ENV': '"test"',
+  },
   test: {
     globals: true,
-    environment: 'jsdom',
+    environment: 'happy-dom',
     setupFiles: ['./src/test/setup.ts'],
     include: ['src/**/*.{test,spec}.{ts,tsx}'],
     css: false,