Ndtyjky

My purpose is simply to test one function. I cannot figure out how to mock firebase properly. I try to keep the example with axios mocking from Jest docs. I have the following code:

MusicService.js

import { initializeApp } from "firebase/app";

import "firebase/database";



const firebase = initializeApp({

  apiKey: "<API_KEY>",

  authDomain: "<PROJECT_ID>.firebaseapp.com",

  databaseURL: "https://<DATABASE_NAME>.firebaseio.com",

  projectId: "<PROJECT_ID>",

  storageBucket: "<BUCKET>.appspot.com",

  messagingSenderId: "<SENDER_ID>",

});



export class MusicService {

  static getAlbums() {

    return firebase.database().ref("albums").once("value")

    .then(snapshot => Object.values(snapshot.val()));

  }

}

MusicService.test.js

import firebase from 'firebase/app';

import 'firebase/database';

import { MusicService } from './MusicService';



jest.mock('firebase/app');

jest.mock('firebase/database');



test("test", () => {

  firebase.initializeApp.mockImplementation(() => {

    database: jest.fn(() => {

      return {

        ref: jest.fn()

      }

    })

  });



  MusicService.getAlbums();

});

The problem is that I get the following error:

I tried to mock firebase.database.

test("test", () => {

  firebase.mockImplementation(() => {

    return {

      database: {



      }

    }

  });

  MusicService.getAlbums();

});

But in this case I get the error that says:

TypeError: _app.default.mockImplementation is not a function.

I don't expect the working example will be given, but rather could you tell please, what exactly should I mock? The whole firebase library or maybe the part where my function starts - return firebase.database().