Firebase Cloud Function - Unit Testing - Please supply a Firebase app in the constructor for DataSnapshot in order to use the .ref method - node.js

Question

I am trying to setup Unit Testing for Firebase cloud functions. I was following these links:
https://firebase.google.com/docs/functions/unit-testing
https://github.com/firebase/functions-samples/blob/4663b4ddfae3ed8f8a110156d60e71f028680ee7/quickstarts/uppercase/functions/test/test.online.js
I am trying to make the sample code run. Code is as follows:
const chai = require('chai');
const sinon = require('sinon');
const admin = require('firebase-admin');
const projectConfig = {
databaseURL : 'https://gr-automation-5e65c.firebaseio.com',
storageBucket : 'gr-automation-5e65c.appspot.com',
projectId : 'gr-automation-5e65c',
};
const test = require('firebase-functions-test')(projectConfig, '../gr-automation-5e65c-firebase-adminsdk-jkdtf-849f3d0f65.json');
test.mockConfig( /* removed for Clarity */ );
const assert = chai.assert;
describe('Cloud Functions', () => {
let myFunctions;
adminInitStub = sinon.stub(admin, 'initializeApp');
admin.initializeApp();
//console.log(test);
before(() => {
myFunctions = require('../lib/index.js');
//console.log(myFunctions);
//console.log(admin);
});
after(() => {
test.cleanup();
admin.database().ref('messages').remove();
});
describe('makeUpperCase', () => {
it('should upper case input and write it to /uppercase', () => {
const snap = test.database.makeDataSnapshot('input', 'messages/11111/original');
const wrapped = test.wrap(myFunctions.makeUppercase);
return wrapped(snap).then(() => {
return admin.database().ref('messages/11111/uppercase').once('value').then((createdSnap) => {
assert.equal(createdSnap.val(), 'INPUT');
});
});
})
});
});
When I run the test, I get the following error:
Cloud Functions
makeUpperCase
Uppercasing undefined input
1) should upper case input and write it to /uppercase
2) "after all" hook
0 passing (364ms)
2 failing
1) Cloud Functions
makeUpperCase
should upper case input and write it to /uppercase:
Error: Please supply a Firebase app in the constructor for DataSnapshot in order to use the .ref method.
at DataSnapshot.get ref [as ref] (node_modules/firebase-functions/lib/providers/database.js:186:19)
at Function.exports.makeUppercase.functions.database.ref.onCreate [as run] (lib/index.js:135:21)
at wrapped (node_modules/firebase-functions-test/lib/main.js:53:30)
at Context.it (test/index.test.js:46:13)
2) Cloud Functions
"after all" hook:
Error: The default Firebase app does not exist. Make sure you call initializeApp() before using any of the Firebase services.
at FirebaseAppError.FirebaseError [as constructor] (node_modules/firebase-admin/lib/utils/error.js:39:28)
at FirebaseAppError.PrefixedFirebaseError [as constructor] (node_modules/firebase-admin/lib/utils/error.js:85:28)
at new FirebaseAppError (node_modules/firebase-admin/lib/utils/error.js:119:28)
at FirebaseNamespaceInternals.app (node_modules/firebase-admin/lib/firebase-namespace.js:105:19)
at FirebaseNamespace.app (node_modules/firebase-admin/lib/firebase-namespace.js:372:30)
at FirebaseNamespace.ensureApp (node_modules/firebase-admin/lib/firebase-namespace.js:388:24)
at FirebaseNamespace.fn (node_modules/firebase-admin/lib/firebase-namespace.js:283:30)
at Context.after (test/index.test.js:31:15)
Any hint on what am I doing wrong?

Answer 1

test.data.makeDataSnapshot has an optional third parameter which is a Firebase app (see https://firebase.google.com/docs/reference/functions/test/test.database#.makeDataSnapshot). However, since you initialized the firebase-functions-test with your project config values, you normally do not need to supply it.
However you have this line:
adminInitStub = sinon.stub(admin, 'initializeApp');
This is causing the next line to initialize a fake app, since initializeApp method was stubbed out to not do anything
This is causing the 2 failures, to fix, remove:
adminInitStub = sinon.stub(admin, 'initializeApp');