Hi!
I have implemented a Node JS app with the authentication guide from Traversy Media on Youtube to implement LocalStrategy with passport. Then i looked into the github repo to see and implement the example from Blizzard implementing Bnet strategy. The application so far will take me to a site where it says:
400 Invalid grant type or callback URL is not valid.
I hosted the app on Heroku apps, but i doubt that the HTTPS protocol from their site (since im using a subdomain to heroku) is enough to use the api perhaps. Or am I into another issue here?
How would I test if the oauth implementation is correct?
EDIT: --------------------------------------------
Resolved!
The issue was exactly what was said there. The callback url was not the same as implemented in the code.
I also confirm I managed to test this correctly live when deplyed to herokuapps via their subdomain as their https works fine to run this with.
So a recommendation to all who wants to “test” their solution, its possible via the heroku deployment. 
Merry christmas!