def expect_output(output)
      if output.respond_to?(:~)
        assert_matching_output(output.to_s, all_output)
      else
        assert_partial_output(output, all_output)
      end
    end
def expect_output(output)
      if output.respond_to?(:~)
        assert_matching_output(output.to_s, all_output)
      else
        assert_partial_output(output, all_output)
      end
    end
Assert that the output contains the specified warning.

 @param [String] output The output to check for.