我想要的是：

class Foo
  private
 
  def bar
    "bar"
  end
 
  magic_private_method_defined_test_method :bar #=> true
end

我尝试过的：

class Foo
  private
 
  def bar
    "bar"
  end
 
  respond_to? :bar #=> false
  #this actually calls respond_to on the class,and so respond_to :superclass gives true
  defined? :bar #=> nil
  instance_methods.include?(:bar) #=> false
  methods.include?(:bar) #=> false
  method_defined?(:bar) #=> false
  def bar
    "redefined!"
  end # redefining doesn't cause an error or anything
 
  public
  def bar
    "redefined publicly!"
  end #causes no error,behaves no differently whether or not #bar had been defined prevIoUsly
end