add respond_to? to ActionDispatch::Integration::Runner

since Runner uses method_missing to delegate to the integration session it also should define respond_to? accordingly

actionpack/lib/action_dispatch/testing/integration.rb

@@ -363,6 +363,10 @@ def url_options
         integration_session.url_options
       end
 
+      def respond_to?(method, include_private = false)
+        @integration_session.respond_to?(method, include_private) || super
+      end
+
       # Delegate unhandled messages to the current session instance.
       def method_missing(sym, *args, &block)
         reset! unless integration_session