The Single-File Rails Application

config.ru

require 'rubygems'
require 'rails'
require 'active_support/railtie'
require 'action_dispatch/railtie'
require 'action_controller/railtie'

class SingleFile < Rails::Application
  config.eager_load = true
  config.cache_classes = true

  config.secret_key_base = 'test'

  routes.append do
    root to: lambda { |env|
      [200, { 'Content-Type' => 'text/plain' }, ['Hello world']]
    }
  end
end

SingleFile.initialize!
run Rails.application