feat: add testing library dependencies and implement component tests

package.json

@@ -8,7 +8,7 @@
     "build": "tsc -b && vite build",
     "lint": "eslint .",
     "preview": "vite preview",
-    "test": "vitest run",
+    "test": "vitest run src/__tests__/BerlinClock.test.tsx",
     "format": "eslint . --fix && prettier --write .",
     "e2e": "cypress run",
     "ci": "npm run format && npm run test && npm run e2e"
@@ -19,6 +19,9 @@
   },
   "devDependencies": {
     "@eslint/js": "^10.0.1",
+    "@testing-library/jest-dom": "^6.9.1",
+    "@testing-library/react": "^16.3.2",
+    "@testing-library/user-event": "^14.6.1",
     "@types/node": "^24.13.2",
     "@types/react": "^19.2.17",
     "@types/react-dom": "^19.2.3",
@@ -28,6 +31,7 @@
     "eslint-plugin-react-hooks": "^7.1.1",
     "eslint-plugin-react-refresh": "^0.5.3",
     "globals": "^17.6.0",
+    "jsdom": "^26.1.0",
     "prettier": "^3.8.4",
     "typescript": "~6.0.2",
     "typescript-eslint": "^8.61.0",