File: //usr/local/rvm/src/ruby-2.5.9/spec/ruby/library/delegate/delegate_class/respond_to_missing_spec.rb
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