• You want to build your application, not Rails
• You might decide to get rid of Rails at some point
• You want to use the same logic from different places
• You want to make your integration tests easier to write
• You want to hide classes and their implementation

• @blog
• @shop
• @intranet
• @cms
• @player

class ApplicationController < ActiveSomething
  helper_method :intranet
  def intranet    @intranet ||= Intranet.new(current_user)
  end
end

class DashboardController  helper_method :dashboard  def dashboard    @dashboard ||= intranet.dashboard  end
  def show    @visits = dashboard.visits.paginate ...  endend

 class Intranet   def dashboard; @dashboard ||= Dashboard.new end
 class Dashboard   def stats      @stats ||= DashboardStats.new   end  end

class FilesController < ApplicationController  def new    @form_model = intranet.files.form  endend

class Intranet  def initialize(user)    @employee = user  end
  def files    @files ||= if user.is_a?(Admin)      FilesManager.new    else      FilesViewer.new    end  endend

class FilesViewer  def files_list  endend 
class FilesBrowser < FilesViewer  def upload_file(file)  end
  def remove_file(filename)  endend

• Testing with real browser is hard and slow
• Write just some end-to-end tests, leave edge cases 
  for integration tests
• Write more integration tests easier