Refactoring + added tests

package.json

@@ -33,12 +33,12 @@
     "jasmine": "^4.0.2",
     "jasmine-spec-reporter": "^7.0.0",
     "supertest": "^6.2.2",
+    "image-size": "^1.0.1",
     "ts-node": "^10.4.0",
     "typescript": "^4.5.4"
   },
   "dependencies": {
     "express": "^4.17.2",
-    "image-size": "^1.0.1",
     "nodemon": "^2.0.15",
     "path": "^0.12.7",
     "sharp": "^0.29.3"