rails の実行モード

■ コード内でモードを取得
Rails - How do I check developer mode or production mode in code
http://stackoverflow.com/questions/6476832/rails-how-do-i-check-developer-mode-or-production-mode-in-code

Rails.env == "production"
Rails.env == "development"
Rails.env.production?
Rails.env.development?

■ 実行時にオプションで指定する
rake db:migrate RAILS_ENV=test
rails s -e production