Add cucumber test for engine routes

Author: drwl

features/request_specs/engine_named_routes.feature

@@ -0,0 +1,83 @@
+Feature: engine named routes
+
+  Generated requeset specs inside a Rails Engine is able to use route and url helpers.
+
+  Scenario: include engine route helpers
+    Given a file named "spec/requests/widgets_spec.rb" with:
+      """ruby
+      require "rails_helper"
+
+      # A very simple Rails engine
+      module MyEngine
+        class Engine < ::Rails::Engine
+          isolate_namespace MyEngine
+        end
+
+        class LinksController < ::ActionController::Base
+          def index
+            render plain: 'hit_engine_route'
+          end
+        end
+      end
+
+      MyEngine::Engine.routes.draw do
+        resources :links, :only => [:index]
+      end
+
+      Rails.application.routes.draw do
+        mount MyEngine::Engine => "/my_engine"
+      end
+
+      module MyEngine
+        RSpec.describe "Links", :type => :request do
+
+          include Engine.routes.url_helpers
+
+          it "redirects to a random widget" do
+            get links_url
+            expect(response.body).to eq('hit_engine_route')
+          end
+        end
+      end
+      """
+    When I run `rspec spec`
+    Then the example should pass
+
+  Scenario: do not include engine route helpers
+    Given a file named "spec/requests/widgets_spec.rb" with:
+      """ruby
+      require "rails_helper"
+
+      # A very simple Rails engine
+      module MyEngine
+        class Engine < ::Rails::Engine
+          isolate_namespace MyEngine
+        end
+
+        class LinksController < ::ActionController::Base
+          def index
+            render plain: 'hit_engine_route'
+          end
+        end
+      end
+
+      MyEngine::Engine.routes.draw do
+        resources :links, :only => [:index]
+      end
+
+      Rails.application.routes.draw do
+        mount MyEngine::Engine => "/my_engine"
+      end
+
+      module MyEngine
+        RSpec.describe "Links", :type => :request do
+
+          it "redirects to a random widget" do
+            get links_url
+            expect(response.body).to eq('hit_engine_route')
+          end
+        end
+      end
+      """
+    When I run `rspec spec`
+    Then the example should fail