Do people have automated tests to validate their SMSs are sent correctly (and received by a real phone)? Or that credit card payments are made correctly? These are things I use third party libraries for, and what I worry might break when I upgrade dependency versions.
I guess the question becomes how far out you want to test. If your credit card processor is a third party they could technically break something, regardless of which version of their library you use. In that case, do you really care that a transaction goes through, or do you just care that you used your third parties interface correctly (be that rest or binary api calls).
If your requirements aren't that sharp, like maybe you can take a day or two to process the credit card payments, you could get away with monitoring your application and configuring alarms for if no transactions go through. That way you'd catch errors originating from your third party as well.
