routed applications will respond to these methods

actionpack/lib/action_dispatch/routing/mapper.rb

@@ -616,7 +616,7 @@ def app_name(app)
           end
 
           def define_generate_prefix(app, name)
-            return unless app.respond_to?(:routes) && app.routes.respond_to?(:define_mounted_helper)
+            return unless app.respond_to?(:routes)
 
             _route = @set.named_routes.routes[name.to_sym]
             _routes = @set

actionpack/lib/action_dispatch/testing/integration.rb

@@ -200,7 +200,7 @@ def url_options
         @url_options ||= default_url_options.dup.tap do |url_options|
           url_options.reverse_merge!(controller.url_options) if controller
 
-          if @app.respond_to?(:routes) && @app.routes.respond_to?(:default_url_options)
+          if @app.respond_to?(:routes)
             url_options.reverse_merge!(@app.routes.default_url_options)
           end