feat: [back] basic testing libraries installed

back-express/package.json

@@ -11,11 +11,17 @@
   "license": "ISC",
   "description": "",
   "devDependencies": {
+    "@types/chai": "^5.2.2",
     "@types/cors": "^2.8.17",
     "@types/express": "^5.0.0",
+    "@types/mocha": "^10.0.10",
     "@types/node": "^22.7.4",
+    "@types/sinon": "^17.0.4",
+    "chai": "^5.2.1",
     "express": "^4.21.0",
+    "mocha": "^11.7.1",
     "nodemon": "^3.1.7",
+    "sinon": "^21.0.0",
     "ts-node": "^10.9.2",
     "typescript": "^5.6.2"
   },