Rails Environments

Rails comes equipped with three environments: test, development, and production. The default environment for the Rails console is development:

  $ rails console
  Loading development environment
  >> Rails.env
  => "development"
  >> Rails.env.development?
  => true
  >> Rails.env.test?
  => false
As you can see, Rails provides a Rails object with an env attribute and associated environment boolean methods, so that, for example, Rails.env.test? returns true in a test environment and false otherwise.

If you ever need to run a console in a different environment (to debug a test, for example), you can pass the environment as a parameter to the console script:

  $ rails console test
  Loading test environment
  >> Rails.env
  => "test"
  >> Rails.env.test?
  => true
As with the console, development is the default environment for the Rails server, but you can also run it in a different environment:

  $ rails server --environment production
If you view your app running in production, it won’t work without a production database, which we can create by running rails db:migrate in production:

  $ rails db:migrate RAILS_ENV=production
(I find it confusing that the idiomatic commands to run the console, server, and migrate commands in non-default environments use different syntax, which is why I bothered showing all three. It’s worth noting, though, that preceding any of them with RAILS_ENV=<env> will also work, as in RAILS_ENV=production rails server).

By the way, if you have deployed your sample app to Heroku, you can see its environment using heroku run console:

  $ heroku run console
  >> Rails.env
  => "production"
  >> Rails.env.production?
  => true
Naturally, since Heroku is a platform for production sites, it runs each application in a production environment.