How can I test my Backend API against google Oauth2? - node.js

Question

My goal is to create an authentication backend and I would like to implement google's Oauth2, and for that I decided to follow the passport documentation. My only issue is, how can I test this on my Postman? I'm just developing a backend and I don't know if it's working, I know it sounds a little silly but for a beginner like me it's a lot. Thanks
const dotenv = require('dotenv').config();
const express = require('express');
const passport = require('passport');
var GoogleStrategy = require('passport-google-oauth20').Strategy;
const app = express();
const port = process.env.PORT;
passport.use(new GoogleStrategy({
clientID: process.env.GOOGLE_CLIENT_ID,
clientSecret: process.env.GOOGLE_CLIENT_SECRET,
callbackURL: "http://www.example.com/auth/google/callback"
},
function(accessToken, refreshToken, profile, cb) {
User.findOrCreate({ googleId: profile.id }, function (err, user) {
return cb(err, user);
});
}
));
app.get('/auth/google',
passport.authenticate('google', { scope: ['profile'] }));
app.get('/auth/google/callback',
passport.authenticate('google', { failureRedirect: '/login' }),
function(req, res) {
res.redirect('/');
});
try {
app.listen(port);
console.log(`Server starting on port ${port}`);
} catch (err) {
console.log(err);
}

Answer 1

Whichever OAuth2 service is pretty simply, if you step into it ;)
In first step you send client_id and client_secret to authorization uri.
In second step, the user authenticates with his credentials and you receive the code which you exchange with authorization server for token.
You make request with Bearer token.
Postman can handle some of the things for you. So:
In Google Dev Console create your credentials.
As callback uri fill in:
https://www.getpostman.com/oauth2/callback
https://oauth.pstmn.io/v1/callback
In Postman create new Collection and define following variables:
Define following Authorization:
When you click Get New Access Token you will be asked to login to Google and get back with token.
With this token you can use whichever service you have in scope and your project on Developer Console includes (look for Enabled APIs and services).
Example request:
Create new GET request and save it in your collection, so the variables and tokens are inherited.
URL is: https://www.googleapis.com/oauth2/v1/userinfo?alt=json
Auth in Postman: Inherit auth from parent.
And Send...
Took me months to understand, so hope you'll be swifter :)