Firestore configuration - Unit testing Cloud Firestore

firebase.json

{
  "emulators": {
    "firestore": {
      "host": "127.0.0.1"
    },
    "functions": {
      "host": "127.0.0.1"
    }
  },
  "firestore": {
    "rules": "rules/firestore.rules"
  },
  "functions": {
    "predeploy": ["yarn build:functions"]
  }
}