> that doesn't mean that the behavior doesn't exist. 

We have a fundamentally different view on what specifications are supposed to do, apparently. The server may respond in some way, yes, but we don't make any guarantees to our customers that it does. It could do absolutely anything. It's true that that _exists_ but that doesn't mean it's _useful_ in any way.

> What happens when you try to charge a card $100mm?

Well, I doubt that anyone has that big of a limit, so it would probably get declined for being over the limit. Which is distinct from 'a card network doesn't support this kind of transaction,' at least in my mind.

> What's supposed to catch that bug other than the scenarios?

Their application's tests? If someone writes bad client code, I can't debug it for them. The error message they display to their users is completely out of the scope of our API.