Authentication Test

I am currently attempting to develop a mobile app that works with my wordpress site through basic authentication with its user’s. I would like to know what would be the best way to test a user’s credentials but do nothing else. That way I can provide a “login screen” where it validates their credentials then stores them on the device if they are valid. So far I have not seen a way to do that in the documentation. Am I just overlooking it or is my approach to this entirely wrong?