# File lib/excon.rb, line 95
    def stub(request_params, response_params = nil)
      if block_given?
        if response_params
          raise(ArgumentError.new("stub requires either response_params OR a block"))
        else
          stub = [request_params, Proc.new]
        end
      elsif response_params
        stub = [request_params, response_params]
      else
        raise(ArgumentError.new("stub requires either response_params OR a block"))
      end
      stubs.unshift(stub)
      stub
    end