Setup for testing HTTP-triggered Firebase Functions locally

testing.js

const functions = require('firebase-functions'); // To stub config()
const admin = require('firebase-admin'); // To get credential cert for initializeApp
const firebase = require('firebase'); // To sign in test user and test database writes
const assert = require('chai').assert;
const sinon = require('sinon');

// https://firebase.google.com/docs/functions/unit-testing

// The functions make use of 'firebase-admin', whereas client-side code uses 'firebase'.
// We initialze 'firebase' here to mock client-side code.
// 'firebase-admin' is only needed here to generate the credential for stubbing 'functions',
// and should not be initialized here.

describe('functions', function () {

  var myFunctions;
  var configStub;
  var authToken;

  before(done => {

    // Load config

    const serviceAccount = require('./config/serviceAccountKey.json');
    const firebaseConfig = require('./config/firebase.json');
    const creds = require('./config/accountCredentials.json');

    // Normally config values are loaded from Cloud Runtime Config;
    // here we'll stub functions.config() with our own testing values
    
    configStub = sinon.stub(functions, 'config').returns({
      firebase: {
        credential: admin.credential.cert(serviceAccount),
        databaseURL: firebaseConfig.databaseURL,
      },
    });

    // Now we can require index.js and save the exports inside a namespace called myFunctions

    myFunctions = require('../index');

    // Now we initialize firebase to sign in and check database values below

    firebase.initializeApp(firebaseConfig);

    // Sign in and get auth token for use during tests
    
    firebase.auth().signInWithEmailAndPassword(creds.email, creds.password).then(user => {
      user.getToken().then(token => {
        authToken = token;
        done();
      });
    });
    
  });

  after(() => {
    
    // Restore our stubs to the original methods
    
    configStub.restore();
    
  });

  it('tests', done => {

    const req = {
      // <ADD QUERY OBJECT>
      headers: { origin: '*' }, // Needed for cors middleware
    };

    const res = {
      status (code) {
        assert.equal(code, 200);
        return this;
      },
      json (json) {
        console.log(json);
        
        // <ADD CODE TO CHECK VALUES WRITTEN TO DATABASE PROPERLY>
        
        done();
      },
      setHeader () {}, // Needed for cors middleware
    }

    // <ADD FUNCTION CALL TO TEST>
    // EXAMPLE: myFunctions.myFunction(req, res);
    
    // http-triggered functions all end with res.status(CODE).json(JSON);

  });

});

FYI getHeader is now required as well

e.g.

      const res = {
        status (code) {
          assert.equal(code, 200);
          return this;
        },
        json (json) {
          console.log(json);
          // <ADD CODE TO CHECK VALUES WRITTEN TO DATABASE PROPERLY>          
          done();
        },
        setHeader () {}, // Needed for cors middleware
        getHeader () {}, // Needed for cors middleware
      }

is the stub functions.configstill relevant?