require 'delegate' describe "DelegateClass#respond_to_missing?" do it "is used for respond_to? behavior of late-bound delegated methods" do # From jruby/jruby#3151: # DelegateClass subtracts Delegate's public API from the target class's instance_methods # to determine which methods to eagerly delegate. If respond_to_missing? shows up in # instance_methods, it will get delegated and skip the delegate-aware implementation # in Delegate. Any methods that must be delegated through method_missing, like methods # defined after the DelegateClass is created, will fail to dispatch properly. cls = Class.new dcls = DelegateClass(cls) cdcls = Class.new(dcls) cdcls_obj = cdcls.new(cls.new) cdcls_obj.respond_to?(:foo).should == false cls.class_eval { def foo; end } cdcls_obj.respond_to?(:foo).should == true end end