Firebase Unit Testing: The default Firebase app does not exist

Question

I try to mock my firebase app but at a point, I don't find a solution to make it work and there is no example in the firebase documentation to make it that way.

In my code, I have this method call to initialize firebase:

ServiceAccount can be a JSON path or the string coming from ENV settings for test purpose

initialize(): void {
    if (!fs.existsSync(this.serviceAccount) && this.serviceAccount) {
        this.serviceAccount = JSON.parse(this.serviceAccount);
    }
    firebaseAdmin.initializeApp({
        credential: firebaseAdmin.credential.cert(this.serviceAccount),
        databaseURL: this.url
    });
    firebaseAdmin.auth();
    firebaseAdmin.database.enableLogging(true);
    this.database = firebaseAdmin.database();
}

Then in my test, wrote this:

certStub = sinon.stub(admin.credential, 'cert').returns('');
firebaseAdminInitStub = sinon.stub(admin, 'initializeApp');
authStub = sinon.stub(admin, 'auth')

firebaseDatabaseStub = sinon.stub(admin, 'database');
firebaseDatabaseStub.get(() => (() => ({ref: refStub})));
refStub.withArgs(FirebaseContact.ref).returns({push: pushStub});
pushStub.withArgs(Contact).returns(Promise.resolve({ref: 'new_ref'}));

// Initialize it for the coming test
firebase.initialize();

Basically, I mostly use their code for the real-time database usage, but for the authenticating part, it gave me the error:

The default Firebase app does not exist. Make sure you call initializeApp() before using any of the Firebase services.

Throwing in :

firebaseAdmin.auth();

Exception:
at FirebaseAppError.FirebaseError [as constructor] (node_modules/firebase-admin/lib/utils/error.js:39:28)
addressBook.app_test |       at FirebaseAppError.PrefixedFirebaseError [as constructor] (node_modules/firebase-admin/lib/utils/error.js:85:28)
addressBook.app_test |       at new FirebaseAppError (node_modules/firebase-admin/lib/utils/error.js:119:28)
addressBook.app_test |       at FirebaseNamespaceInternals.Object.<anonymous>.FirebaseNamespaceInternals.app (node_modules/firebase-admin/lib/firebase-namespace.js:105:19)
addressBook.app_test |       at FirebaseNamespace.Object.<anonymous>.FirebaseNamespace.app (node_modules/firebase-admin/lib/firebase-namespace.js:372:30)
addressBook.app_test |       at FirebaseNamespace.Object.<anonymous>.FirebaseNamespace.ensureApp (node_modules/firebase-admin/lib/firebase-namespace.js:388:24)
addressBook.app_test |       at FirebaseNamespace.fn (node_modules/firebase-admin/lib/firebase-namespace.js:268:30)
addressBook.app_test |       at Firebase.initialize (src/firebase/firebase.ts:29:23)
addressBook.app_test |       at Object.done (src/tests/api/contact.test.ts:43:18)

What I know, initializeApp should be called to create the app, but as it has been stub (according to the example) it can create an app. So Should I try to stub the auth part or use the initializeApp differently ?

Any idea ? :(

Answer 1

To make it work I have to refactor my initialize method and move out the config to:

initialize(): void {
    if (!fs.existsSync(this.serviceAccount) && this.serviceAccount) {
        this.serviceAccount = JSON.parse(this.serviceAccount);
    }
    firebaseAdmin.initializeApp(this.getConfig());
    firebaseAdmin.auth();
    this.database = firebaseAdmin.database();
}

getConfig(): Object {
    return {
        credential: firebaseAdmin.credential.cert(this.serviceAccount),
        databaseURL: this.url
    };
}

Then, I was able to stub the getConfig like they use in the firebase example, but without stubbing the initializeApp (It wasn't working with), here is my beforeAll:

getConfigStub = sinon.stub(firebase, 'getConfig');
getConfigStub.callsFake(() => {});
getConfigStub.returns({
    firebase: {
        databaseURL: 'https://not-a-project.firebaseio.com',
        storageBucket: 'not-a-project.appspot.com',
    }
});

firebaseDatabaseStub = sinon.stub(admin, 'database');
firebaseDatabaseStub.get(() => (() => ({ref: refStub})));
refStub.withArgs(FirebaseContact.ref).returns({push: pushStub});

My firebase variable could make you think it comes from the import of the package, it's not. It's my Firebase class used to wrap my logic. see:

import * as fs from 'fs';
import * as firebase from 'firebase';
import * as firebaseAdmin from 'firebase-admin';

import { FirebaseInterface } from './firebaseInterface';

export class Firebase implements FirebaseInterface {
    private database: firebaseAdmin.database.Database;

    /**
     * Constructor
     * @param {string} serviceAccount
     * @param {string} url
     */
    constructor(private serviceAccount: string, private url: string) {}

    /**
     * Initialize connection
     * @returns {firebase.database.Reference}
     */
    initialize(): void {
        if (!fs.existsSync(this.serviceAccount) && this.serviceAccount) {
            this.serviceAccount = JSON.parse(this.serviceAccount);
        }
        firebaseAdmin.initializeApp(this.getConfig());
        firebaseAdmin.auth();
        this.database = firebaseAdmin.database();
    }

    getConfig(): Object {
        return {
            credential: firebaseAdmin.credential.cert(this.serviceAccount),
            databaseURL: this.url
        };
    }

    /**
     * Get ref
     * @returns {firebase.database.Reference}
     */
    getDatabase(): firebaseAdmin.database.Database {
        return this.database;
    }
}