3 files changed, 14 insertions, 6 deletions
diff --git a/actionpack/test/controller/integration_test.rb b/actionpack/test/controller/integration_test.rb
index 214eab2f0d..78cce3aa64 100644
--- a/actionpack/test/controller/integration_test.rb
+++ b/actionpack/test/controller/integration_test.rb
@@ -1,6 +1,7 @@
 require 'abstract_unit'
 require 'controller/fake_controllers'
 require 'action_view/vendor/html-scanner'
+require 'rails/engine'
 
 class SessionTest < ActiveSupport::TestCase
   StubApp = lambda { |env|
@@ -595,7 +596,7 @@ class ApplicationIntegrationTest < ActionDispatch::IntegrationTest
     @routes ||= ActionDispatch::Routing::RouteSet.new
   end
 
-  class MountedApp
+  class MountedApp < Rails::Engine
     def self.routes
       @routes ||= ActionDispatch::Routing::RouteSet.new
     end
diff --git a/actionpack/test/dispatch/mount_test.rb b/actionpack/test/dispatch/mount_test.rb
index ff4b644c16..d5a4d8ee11 100644
--- a/actionpack/test/dispatch/mount_test.rb
+++ b/actionpack/test/dispatch/mount_test.rb
@@ -1,12 +1,18 @@
 require 'abstract_unit'
+require 'rails/engine'
 
 class TestRoutingMount < ActionDispatch::IntegrationTest
   Router = ActionDispatch::Routing::RouteSet.new
 
-  class FakeEngine
+  class AppWithRoutes < Rails::Engine
     def self.routes
       @routes ||= ActionDispatch::Routing::RouteSet.new
     end
+  end
+
+  # Test for mounting apps that respond to routes, but aren't Rails-like apps.
+  class SinatraLikeApp
+    def self.routes; Object.new; end
 
     def self.call(env)
       [200, {"Content-Type" => "text/html"}, ["OK"]]
@@ -21,15 +27,15 @@ class TestRoutingMount < ActionDispatch::IntegrationTest
     mount SprocketsApp, :at => "/sprockets"
     mount SprocketsApp => "/shorthand"
 
-    mount FakeEngine, :at => "/fakeengine", :as => :fake
-    mount FakeEngine, :at => "/getfake", :via => :get
+    mount SinatraLikeApp, :at => "/fakeengine", :as => :fake
+    mount SinatraLikeApp, :at => "/getfake", :via => :get
 
     scope "/its_a" do
       mount SprocketsApp, :at => "/sprocket"
     end
 
     resources :users do
-      mount FakeEngine, :at => "/fakeengine", :as => :fake_mounted_at_resource
+      mount AppWithRoutes, :at => "/fakeengine", :as => :fake_mounted_at_resource
     end
 
     mount SprocketsApp, :at => "/", :via => :get
diff --git a/actionpack/test/dispatch/prefix_generation_test.rb b/actionpack/test/dispatch/prefix_generation_test.rb
index cd31e8e326..c6e4eefa7a 100644
--- a/actionpack/test/dispatch/prefix_generation_test.rb
+++ b/actionpack/test/dispatch/prefix_generation_test.rb
@@ -1,5 +1,6 @@
 require 'abstract_unit'
 require 'rack/test'
+require 'rails/engine'
 
 module TestGenerationPrefix
   class Post
@@ -23,7 +24,7 @@ module TestGenerationPrefix
   class WithMountedEngine < ActionDispatch::IntegrationTest
     include Rack::Test::Methods
 
-    class BlogEngine
+    class BlogEngine < Rails::Engine
       def self.routes
         @routes ||= begin
           routes = ActionDispatch::Routing::RouteSet.new