+ t = unit_name_replace_instance("foo@.service", "waldo");
+ puts(t);
+ free(t);
+
+ t = unit_name_replace_instance("foo@xyz.service", "waldo");
+ puts(t);
+ free(t);
+
+ t = unit_name_replace_instance("xyz", "waldo");
+ puts(t);
+ free(t);
+
+ t = unit_name_replace_instance("", "waldo");
+ puts(t);
+ free(t);
+
+ t = unit_name_replace_instance("", "");
+ puts(t);
+ free(t);
+
+ t = unit_name_replace_instance("foo.service", "waldo");
+ puts(t);
+ free(t);
+