add coverage in tests

Author: BarbDMC

package.json

@@ -4,7 +4,7 @@
   "description": "",
   "main": "app.ts",
   "scripts": {
-    "test": "NODE_OPTIONS=--experimental-vm-modules jest",
+    "test": "NODE_OPTIONS=--experimental-vm-modules jest --coverage",
     "dev": "nodemon --exec ts-node ./app.ts",
     "start": "node app.js"
   },