module CustomMatchers
  class OnlyHaveAttributesMatcher
    
    def initialize(*attrs)  
      @attributes = attrs.map(&:to_s)
    end  
  
    def matches?(target)  
      @target_attributes = target.keys.map(&:to_s)
      @target_attributes == @attributes
    end  
  
    def failure_message_for_should  
      "expected to only allow attributes #{@attributes.join(", ")}, allowed #{@target_attributes.join(", ")}"
    end  
  
    def failure_message_for_should_not  
      "expected to not only allow attributes #{@attributes.join(", ")}, allowed #{@target_attributes.join(", ")}"
    end  
    
  end  
  
  def only_have_attributes(*attrs)  
    OnlyHaveAttributesMatcher.new(*attrs)  
  end  
end