- Its interface for http integration is a Rack. Sinatra#call(env) that returns [status, headers, body] How simple is that? It's hard to beat.
- Any Rack based web app is so easy to test. Out of container test is baked in from the birth.
How do I set Cache-Control headers for static files?
Enter Rack middleware which is essentially a filter. All I had to do was to write a simple CustomHeaderFilter riding on the same simple Rack interface, another happy day :)