Test domains when registered and unregistered

Fix bug assigning to unknown type.

macaddr_array.go

@@ -82,6 +82,7 @@ func (src *MacaddrArray) AssignTo(dst interface{}) error {
 			if nextDst, retry := GetAssignToDstType(dst); retry {
 				return src.AssignTo(nextDst)
 			}
+			return errors.Errorf("unable to assign to %T", dst)
 		}
 	case Null:
 		return NullAssignTo(dst)