protected.rb

class Node
  def eval(other)
    other.protected_method(self)
  end

protected

  def protected_method(other)
    other
  end
end

class NodeFake
  def initialize(node)
    @node = node
  end

  def eval(other)
    p :pre
    p self == other.protected_method(self)
    p :post
  end
end

NodeFake.new(Node.new).eval(Node.new)