respond_to_visibility_issue.rb

class A
  # There is Kernel#public_method, so we don't want this one to clash
  def pub_method; :public_method; end

  def undefed_method; :undefed_method; end
  undef_method :undefed_method

  protected
  def protected_method; :protected_method; end

  private
  def private_method; :private_method; end

  public
  define_method(:defined_method) { :defined }
end

p A.new.respond_to?(:protected_method, false)