diff --git a/railties/lib/rails/application.rb b/railties/lib/rails/application.rb
index 9e41210119..3ed34f21a6 100644
--- a/railties/lib/rails/application.rb
+++ b/railties/lib/rails/application.rb
@@ -9,7 +9,7 @@ module Rails
     autoload :Configurable,   'rails/application/configurable'
     autoload :Configuration,  'rails/application/configuration'
     autoload :Finisher,       'rails/application/finisher'
-    autoload :Metal,          'rails/application/metal'
+    autoload :MetalLoader,    'rails/application/metal_loader'
     autoload :Railties,       'rails/application/railties'
     autoload :RoutesReloader, 'rails/application/routes_reloader'
 
@@ -51,8 +51,12 @@ module Rails
       @railties ||= Railties.new(config)
     end
 
+    def metal_loader
+      @metal_laoder ||= MetalLoader.new
+    end
+
     def routes_reloader
-      @routes_reloader ||= RoutesReloader.new(config)
+      @routes_reloader ||= RoutesReloader.new
     end
 
     def reload_routes!
diff --git a/railties/lib/rails/application/finisher.rb b/railties/lib/rails/application/finisher.rb
index d67420938a..c0b16a0090 100644
--- a/railties/lib/rails/application/finisher.rb
+++ b/railties/lib/rails/application/finisher.rb
@@ -15,9 +15,9 @@ module Rails
         end
       end
 
-      initializer :add_builtin_route do
+      initializer :add_builtin_route do |app|
         if Rails.env.development?
-          Rails::Application::RoutesReloader.paths << File.join(RAILTIES_PATH, 'builtin', 'routes.rb')
+          app.routes_reloader.paths << File.join(RAILTIES_PATH, 'builtin', 'routes.rb')
         end
       end
 
diff --git a/railties/lib/rails/application/metal.rb b/railties/lib/rails/application/metal_loader.rb
similarity index 70%
rename from railties/lib/rails/application/metal.rb
rename to railties/lib/rails/application/metal_loader.rb
index 17786dd4ba..c0f2e4f948 100644
--- a/railties/lib/rails/application/metal.rb
+++ b/railties/lib/rails/application/metal_loader.rb
@@ -2,20 +2,34 @@ require 'action_dispatch'
 
 module Rails
   class Application
-    class Metal
-      def self.paths
-        @paths ||= []
+    class MetalLoader
+      attr_reader :paths, :metals
+
+      def initialize
+        @paths, @metals = [], []
       end
 
-      def self.metals
-        @metals ||= []
+      def build_middleware(list=nil)
+        load_metals!(list)
+        self
       end
 
-      def initialize(list=nil)
+      def new(app)
+        ActionDispatch::Cascade.new(@metals, app)
+      end
+
+      def name
+        ActionDispatch::Cascade.name
+      end
+      alias :to_s :name
+
+    protected
+
+      def load_metals!(list)
         metals = []
-        list   = Array(list || :all).map(&:to_sym)
+        list = Array(list || :all).map(&:to_sym)
 
-        self.class.paths.each do |path|
+        paths.each do |path|
           matcher = /\A#{Regexp.escape(path)}\/(.*)\.rb\Z/
           Dir.glob("#{path}/**/*.rb").sort.each do |metal_path|
             metal = metal_path.sub(matcher, '\1').to_sym
@@ -30,17 +44,7 @@ module Rails
         end
 
         @metals = metals.map { |m| m.to_s.camelize.constantize }
-        self.class.metals.concat(@metals)
       end
-
-      def new(app)
-        ActionDispatch::Cascade.new(@metals, app)
-      end
-
-      def name
-        ActionDispatch::Cascade.name
-      end
-      alias_method :to_s, :name
     end
   end
 end
diff --git a/railties/lib/rails/application/routes_reloader.rb b/railties/lib/rails/application/routes_reloader.rb
index fe0cfb7801..fde6211c5d 100644
--- a/railties/lib/rails/application/routes_reloader.rb
+++ b/railties/lib/rails/application/routes_reloader.rb
@@ -1,19 +1,16 @@
 module Rails
   class Application
-    # TODO Write tests for this behavior extracted from Application
     class RoutesReloader
-      def self.paths
-        @paths ||= []
-      end
+      attr_reader :paths
 
-      def initialize(config)
-        @config, @last_change_at = config, nil
+      def initialize
+        @paths, @last_change_at = [], nil
       end
 
       def changed_at
         routes_changed_at = nil
 
-        self.class.paths.each do |path|
+        paths.each do |path|
           config_changed_at = File.stat(path).mtime
 
           if routes_changed_at.nil? || config_changed_at > routes_changed_at
@@ -29,7 +26,7 @@ module Rails
         routes.disable_clear_and_finalize = true
 
         routes.clear!
-        self.class.paths.each { |path| load(path) }
+        paths.each { |path| load(path) }
         routes.finalize!
 
         nil
diff --git a/railties/lib/rails/configuration.rb b/railties/lib/rails/configuration.rb
index 0cf39636ac..6d5fa87439 100644
--- a/railties/lib/rails/configuration.rb
+++ b/railties/lib/rails/configuration.rb
@@ -16,7 +16,7 @@ module Rails
           middleware.use('::ActionDispatch::Cookies')
           middleware.use(lambda { ActionController::Base.session_store }, lambda { ActionController::Base.session_options })
           middleware.use('::ActionDispatch::Flash', :if => lambda { ActionController::Base.session_store })
-          middleware.use(lambda { Rails::Application::Metal.new(Rails.application.config.metals) }, :if => lambda { Rails::Application::Metal.metals.any? })
+          middleware.use(lambda { Rails.application.metal_loader.build_middleware(Rails.application.config.metals) }, :if => lambda { Rails.application.metal_loader.metals.any? })
           middleware.use('ActionDispatch::ParamsParser')
           middleware.use('::Rack::MethodOverride')
           middleware.use('::ActionDispatch::Head')
diff --git a/railties/lib/rails/engine.rb b/railties/lib/rails/engine.rb
index ebbee67cf4..b98393c01a 100644
--- a/railties/lib/rails/engine.rb
+++ b/railties/lib/rails/engine.rb
@@ -70,9 +70,9 @@ module Rails
       config.load_once_paths.freeze
     end
 
-    initializer :add_routing_paths do
+    initializer :add_routing_paths do |app|
       paths.config.routes.to_a.each do |route|
-        Rails::Application::RoutesReloader.paths.unshift(route) if File.exists?(route)
+        app.routes_reloader.paths.unshift(route) if File.exists?(route)
       end
     end
 
@@ -98,8 +98,8 @@ module Rails
       ActionMailer::Base.view_paths.unshift(*views)     if defined?(ActionMailer)
     end
 
-    initializer :add_metals do
-      Rails::Application::Metal.paths.unshift(*paths.app.metals.to_a)
+    initializer :add_metals do |app|
+      app.metal_loader.paths.unshift(*paths.app.metals.to_a)
     end
 
     initializer :load_application_initializers do