title: Multiple environments for Ruby application
body: <p>I've been writing Rails apps for so long that I'm suddenly stuck with something you get for free with Rails: environments.</p>
  
  <p>That is to say, you can run the Rails app locally and by default, RAILS_ENV (or Rails.env) is "development". And if you are running your specs/tests, it's "test" and when you deploy to your production server, you set it up to run as "production".</p>
  
  <p>This is particularly useful when you have config files. Also useful for the Gemfile to differentiate gems for certain environments.</p>
  
  <p>So now to my question: I'm writing a pure Ruby app and I don't know the best way to set it up so that I can still have the multiple environments?  I want to set up config files for 3rd-party services (like MongoLab/Iron.IO/etc.) but I want them set up with "development", "test", "production", etc.  And then I want to be able to run the app from various environments.</p>
  
  <p>I know I could just manually handle it via command-line environment variables, but I'm wondering if there are best (better?) practices for this? Any gems that help with this? Or any recommendations for how to structure environment handling for a pure Ruby app?</p>
  
  <p>Thanks,</p>