How to run Ruby app on localhost with Apache 2 and mod_passenger on OS X?

Question

ruby

I apologize for the stupid question, I did not find information on the issue.
When I'm ready to run the Sinatra application on the local machine, I just type into the terminal ruby app.rb. Everything works fine without config.ru . When I deploy to the server, it’s easy for me to launch it service apache2 restartand the local mod_passenger picks up config.ru and launches the app without unnecessary intervention.
Question: how to do the same as on the server, on the local machine on which Apache 2 and mod_passenger are installed, config.ru is present , and all this is in OS X.