App Store Server Notifications Setup/Help

Hello - i'm transitioning my App from paid only to subscription model. I've been able to test in sandbox and parse the Receipt from Apple. Next is the App Store Server Notifications, i setup URL in App Store Connect. But now I need to see what this payload from Apple looks like so I can handle it.

This seems like very hard to test, correct? What I did was setup a POST endpoint in my python backend after I liked . I ended up using libary I found https://pypi.org/project/app-store-notifications-v2-validator/. Does anyone have any tips on how to test these notifications from Apple?