I recently watched a fantastic talk by Nate Barbettini about OAuth 2.0 and Open ID Connect on YouTube. Besides explaining what these protocols are, Nate also showed two useful tools he built for Debugging OAuth 2.0 and Open ID Connect.

The OAuth 2.0 Debugger and the Open ID Connect Debugger are Web Apps, which helpts you setting up and testing OAuth flows without the need of programming your own login around it.