class MyParentClass
  def method_
    p 'test'
  end
end
=> :method_
class ChildClass < DelegateClass(MyParentClass)
end

c = ChildClass.new(MyParentClass.new) #=> #<MyParentClass:0x007ffcaaab0280>
c.class #=> ChildClass
c.method_ #=> "test"
c.respond_to?(:method_) #=> true