I think view-free is a bit of a misnomer. Even in sinatra, you could consider JSON as a "view". You can still test that too with browser plugins like "REST client" for firefox or htty on the command-line.

What it forces you do to is make sure your API is very clean, very succinct and exposes all critical portions of the backend.

Really all we're talking about is the model being a REST service instead of a database model.