Where to put default_url_options

default_url_options.rb

require 'action_controller/railtie'
require 'minitest/autorun'

class RoutingApp < Rails::Application
  config.eager_load = false
  config.root = File.dirname(__FILE__)
  config.session_store :cookie_store, key: 'session'
  config.secret_key_base = 'secret'
end

RoutingApp.initialize!

RoutingApp.routes.draw do
  default_url_options host: 'routes.rb'

  root to: 'pages#index'
end

class Foo
  include Rails.application.routes.url_helpers
end

class Bar
  include Rails.application.routes.url_helpers

  def default_url_options
    { host: 'job.rb' }
  end
end

require 'rails/test_help'

class RoutingTest < ActiveSupport::TestCase
  def test_default_url_options_in_routes_rb
    assert_equal 'http://routes.rb/', Rails.application.routes.url_helpers.root_url
  end

  def test_default_url_options_in_class
    assert_equal 'http://routes.rb/', Foo.new.root_url
  end

  def test_overriding_default_url_options_in_class
    assert_equal 'http://job.rb/', Bar.new.root_url
  end
end