t.Errorf("got wrong error: %v (expected %q)", err, tc.error)
				}
			}
		})
	}
}

// orderByCommentServiceName is a helper function that orders two IPTables rules
// based on the service name in their comment. (If either rule has no comment then the
// return value is undefined.)
func orderByCommentServiceName(rule1, rule2 *iptablestest.Rule) bool {
	if rule1.Comment == nil || rule2.Comment == nil {
		return false
	}