diff --git a/unit/test-hfp.c b/unit/test-hfp.c
index 5218a2b..adc600b 100644
--- a/unit/test-hfp.c
+++ b/unit/test-hfp.c
@@ -51,6 +51,7 @@ struct test_pdu {
 struct test_data {
 	char *test_name;
 	struct test_pdu *pdu_list;
+	hfp_result_func_t result_func;
 };
 
 #define data(args...) ((const unsigned char[]) { args })
@@ -83,7 +84,7 @@ struct test_data {
 		.fragmented = true,				\
 	}
 
-#define define_test(name, function, args...)				\
+#define define_test(name, function, result_function, args...)		\
 	do {								\
 		const struct test_pdu pdus[] = {			\
 			args, { }					\
@@ -91,6 +92,7 @@ struct test_data {
 		static struct test_data data;				\
 		data.test_name = g_strdup(name);			\
 		data.pdu_list = g_malloc(sizeof(pdus));			\
+		data.result_func = result_function;			\
 		memcpy(data.pdu_list, pdus, sizeof(pdus));		\
 		g_test_add_data_func(name, &data, function);		\
 	} while (0)
@@ -252,9 +254,11 @@ static void test_register(gconstpointer data)
 	ret = hfp_gw_set_close_on_unref(context->hfp, true);
 	g_assert(ret);
 
-	ret = hfp_gw_register(context->hfp, prefix_handler, (char *)pdu->data,
-								context, NULL);
-	g_assert(ret);
+	if (context->data->result_func) {
+		ret = hfp_gw_register(context->hfp, context->data->result_func,
+					(char *)pdu->data, context, NULL);
+		g_assert(ret);
+	}
 
 	pdu = &context->data->pdu_list[context->pdu_offset++];
 
@@ -302,42 +306,42 @@ int main(int argc, char *argv[])
 {
 	g_test_init(&argc, &argv, NULL);
 
-	define_test("/hfp/test_init", test_init, data_end());
-	define_test("/hfp/test_cmd_handler_1", test_command_handler,
+	define_test("/hfp/test_init", test_init, NULL, data_end());
+	define_test("/hfp/test_cmd_handler_1", test_command_handler, NULL,
 			raw_pdu('A', 'T', '+', 'B', 'R', 'S', 'F', '\r'),
 			raw_pdu('A', 'T', '+', 'B', 'R', 'S', 'F'),
 			data_end());
-	define_test("/hfp/test_cmd_handler_2", test_command_handler,
+	define_test("/hfp/test_cmd_handler_2", test_command_handler, NULL,
 			raw_pdu('A', 'T', 'D', '1', '2', '3', '4', '\r'),
 			raw_pdu('A', 'T', 'D', '1', '2', '3', '4'),
 			data_end());
-	define_test("/hfp/test_register_1", test_register,
+	define_test("/hfp/test_register_1", test_register, prefix_handler,
 			raw_pdu('+', 'B', 'R', 'S', 'F', '\0'),
 			raw_pdu('A', 'T', '+', 'B', 'R', 'S', 'F', '\r'),
 			type_pdu(HFP_GW_CMD_TYPE_COMMAND, 0),
 			data_end());
-	define_test("/hfp/test_register_2", test_register,
+	define_test("/hfp/test_register_2", test_register, prefix_handler,
 			raw_pdu('+', 'B', 'R', 'S', 'F', '\0'),
 			raw_pdu('A', 'T', '+', 'B', 'R', 'S', 'F', '=', '\r'),
 			type_pdu(HFP_GW_CMD_TYPE_SET, 0),
 			data_end());
-	define_test("/hfp/test_register_3", test_register,
+	define_test("/hfp/test_register_3", test_register, prefix_handler,
 			raw_pdu('+', 'B', 'R', 'S', 'F', '\0'),
 			raw_pdu('A', 'T', '+', 'B', 'R', 'S', 'F', '?', '\r'),
 			type_pdu(HFP_GW_CMD_TYPE_READ, 0),
 			data_end());
-	define_test("/hfp/test_register_4", test_register,
+	define_test("/hfp/test_register_4", test_register, prefix_handler,
 			raw_pdu('+', 'B', 'R', 'S', 'F', '\0'),
 			raw_pdu('A', 'T', '+', 'B', 'R', 'S', 'F', '=', '?',
 									'\r'),
 			type_pdu(HFP_GW_CMD_TYPE_TEST, 0),
 			data_end());
-	define_test("/hfp/test_register_5", test_register,
+	define_test("/hfp/test_register_5", test_register, prefix_handler,
 			raw_pdu('D', '\0'),
 			raw_pdu('A', 'T', 'D', '1', '2', '3', '4', '5', '\r'),
 			type_pdu(HFP_GW_CMD_TYPE_SET, 0),
 			data_end());
-	define_test("/hfp/test_fragmented_1", test_fragmented,
+	define_test("/hfp/test_fragmented_1", test_fragmented, NULL,
 			frg_pdu('A'), frg_pdu('T'), frg_pdu('+'), frg_pdu('B'),
 			frg_pdu('R'), frg_pdu('S'), frg_pdu('F'), frg_pdu('\r'),
 			data_end());