func TestRule(t *testing.T) {
	a := []Rule{&AtRule{}, &QualifiedRule{}}
	for _, r := range a {
		r.rule()
	}
}
Ensure that all rules implement the Rule interface.
package css
import (
	"reflect"
	"testing"
)
func TestNode(t *testing.T) {
	var a []Node
	a = append(a, &StyleSheet{}, &AtRule{}, &QualifiedRule{}, &Declaration{})
	a = append(a, &SimpleBlock{}, &Function{}, &Token{})
	a = append(a, Rules{}, Declarations{}, ComponentValues{})
	for _, n := range a {
		n.node()
	}
}