Sorry, this is bad advice. If you test against 3rd-party systems, eventually your system will grow to the point where you are spending a good deal of time deali

Sorry, this is bad advice. If you test against 3rd-party systems, eventually your system will grow to the point where you are spending a good deal of time dealing with your 3rd-party's random breakage (downtime or flakiness rather than API changes). I learned this lesson twice the hard way: once with social media networks like Twitter and Facebook, and the other with Google Drive.