hnb-test: parse_mm: assert MM pdisc
diff --git a/src/tests/hnb-test.c b/src/tests/hnb-test.c
index 33a3ef3..76f20b8 100644
--- a/src/tests/hnb-test.c
+++ b/src/tests/hnb-test.c
@@ -255,6 +255,8 @@
 	}
 	length -= (const char *)&gh->data[0] - (const char *)gh;
 
+	OSMO_ASSERT(gsm48_hdr_pdisc(gh) == GSM48_PDISC_MM);
+
 	parse_res = tlv_parse(&tp, &gsm48_mm_att_tlvdef, &gh->data[0], length, 0, 0);
 	if (parse_res <= 0) {
 		uint8_t msg_type = gsm48_hdr_msg_type(gh);