tests: appease -Wwrite-strings

tests/test_deep_copy.c

@@ -186,7 +186,8 @@ int main(int argc, char **argv)
 	printf("\nTesting deep_copy with a custom serializer set\n");
 	json_object *with_serializer = json_object_new_string("notemitted");
 
-	json_object_set_serializer(with_serializer, my_custom_serializer, "dummy userdata", NULL);
+	char udata[] = "dummy userdata";
+	json_object_set_serializer(with_serializer, my_custom_serializer, udata, NULL);
 	json_object_object_add(src1, "with_serializer", with_serializer);
 	dst1 = NULL;
 	/* With a custom serializer in use, a custom shallow_copy function must also be used */

tests/test_double_serializer.c

@@ -11,16 +11,17 @@
 int main()
 {
 	struct json_object *obj = json_object_new_double(0.5);
+	char udata[] = "test";
 
 	printf("Test default serializer:\n");
 	printf("obj.to_string(standard)=%s\n", json_object_to_json_string(obj));
 
 	printf("Test default serializer with custom userdata:\n");
-	obj->_userdata = "test";
+	obj->_userdata = udata;
 	printf("obj.to_string(userdata)=%s\n", json_object_to_json_string(obj));
 
 	printf("Test explicit serializer with custom userdata:\n");
-	json_object_set_serializer(obj, json_object_double_to_json_string, "test", NULL);
+	json_object_set_serializer(obj, json_object_double_to_json_string, udata, NULL);
 	printf("obj.to_string(custom)=%s\n", json_object_to_json_string(obj));
 
 	printf("Test reset serializer:\n");