Thank for the prompt reply!
I have the service started (on Postgres.app, the “stop” button is enabled).
If I ran $createuser --createdb --superuser postgres on terminal, I got
createuser: error: creation of new role failed: ERROR: role "postgres" already exists error so the service should be up and running.
And are you using RubyMine for debugging Ruby on Rails code or something else? We just need a debug IDE and doesn’t matter what tool as long as we can have one.