In my experience, payment processors (and related services) are somewhat unique in providing test gateways & APIs. They are also somewhat unique in that they h

In my experience, payment processors (and related services) are somewhat unique in providing test gateways & APIs. They are also somewhat unique in that they handle real money. You don't need a simulated API if you're sending an email or SMS message to a designated recipient or downloading the local weather forecast or traffic news, because there are no significant and irreversible consequences to these actions anyway.