diff --git a/tests/iuup/iuup_test.c b/tests/iuup/iuup_test.c
new file mode 100644
index 0000000..8f32a95
--- /dev/null
+++ b/tests/iuup/iuup_test.c
@@ -0,0 +1,166 @@
+#include <stdint.h>
+#include <string.h>
+
+#include <osmocom/core/msgb.h>
+#include <osmocom/core/application.h>
+#include <osmocom/core/logging.h>
+
+#include <osmocom/mgcp/iuup_cn_node.h>
+#include <osmocom/mgcp/iuup_protocol.h>
+
+void *ctx = NULL;
+
+static const char *dump(struct msgb *msg)
+{
+	return osmo_hexdump_nospc(msg->data, msg->len);
+}
+
+struct msgb *msgb_from_hex(const char *label, const char *hex)
+{
+	struct msgb *msg = msgb_alloc_headroom(4096 + OSMO_IUUP_HEADROOM,
+					       OSMO_IUUP_HEADROOM, label);
+	unsigned char *rc;
+	msg->l2h = msg->data;
+	rc = msgb_put(msg, osmo_hexparse(hex, msg->data, msgb_tailroom(msg)));
+	OSMO_ASSERT(rc == msg->l2h);
+	return msg;
+}
+
+const char *expect_rx_payload = NULL;
+int rx_payload(struct msgb *msg, void *node_priv, void *pdu_priv)
+{
+	printf("rx_payload() invoked by iuup_cn!\n");
+	printf("        [IuUP] -RTP->\n");
+	printf("%s\n", dump(msg));
+	printf("node_priv=%p pdu_priv=%p\n", node_priv, pdu_priv);
+	if (!expect_rx_payload) {
+		printf("ERROR: did not expect rx_payload()\n");
+		exit(-1);
+	} else if (strcmp(expect_rx_payload, dump(msg))) {
+		printf("ERROR: mismatches expected msg %s\n", expect_rx_payload);
+		exit(-1);
+	} else
+		printf("ok: matches expected msg\n");
+	msgb_free(msg);
+	expect_rx_payload = NULL;
+	return 0;
+}
+
+const char *expect_tx_msg = NULL;
+int tx_msg(struct msgb *msg, void *node_priv, void *pdu_priv)
+{
+	printf("tx_msg() invoked by iuup_cn!\n");
+	printf(" <-PDU- [IuUP]\n");
+	printf("%s\n", dump(msg));
+	printf("node_priv=%p pdu_priv=%p\n", node_priv, pdu_priv);
+	if (!expect_tx_msg) {
+		printf("ERROR: did not expect tx_msg()\n");
+		exit(-1);
+	} else if (strcmp(expect_tx_msg, dump(msg))) {
+		printf("ERROR: mismatches expected msg %s\n", expect_tx_msg);
+		exit(-1);
+	} else
+		printf("ok: matches expected msg\n");
+	msgb_free(msg);
+	expect_tx_msg = NULL;
+	return 0;
+}
+
+static int rx_pdu(struct osmo_iuup_cn *cn, struct msgb *msg, void *pdu_priv)
+{
+	int rc;
+	printf(" -PDU-> [IuUP]\n");
+	printf("%s\n", dump(msg));
+	printf("pdu_priv=%p\n", pdu_priv);
+	rc = osmo_iuup_cn_rx_pdu(cn, msg, pdu_priv);
+	printf("rc=%d\n", rc);
+	return rc;
+}
+
+static int tx_payload(struct osmo_iuup_cn *cn, struct msgb *msg, void *pdu_priv)
+{
+	int rc;
+	printf("        [IuUP] <-RTP-\n");
+	printf("%s\n", dump(msg));
+	printf("pdu_priv=%p\n", pdu_priv);
+	rc = osmo_iuup_cn_tx_payload(cn, msg, pdu_priv);
+	printf("rc=%d\n", rc);
+	return rc;
+}
+
+void test_cn_session()
+{
+	void *node_priv = (void*)0x2342;
+	void *pdu_priv = (void*)0xfeed;
+
+	struct osmo_iuup_cn_cfg cfg = {
+		.node_priv = node_priv,
+		.rx_payload = rx_payload,
+		.tx_msg = tx_msg,
+	};
+
+	struct osmo_iuup_cn *cn = osmo_iuup_cn_init(ctx, &cfg, __func__);
+	OSMO_ASSERT(cn);
+
+	printf("\nSend IuUP Initialization. Expecting direct tx_msg() of the Initialization Ack\n");
+	expect_tx_msg = "e400240000";
+	rx_pdu(cn,
+	       msgb_from_hex("IuUP-Init",
+			     "8060dc5219495e3f00010111" /* <- RTP header */
+			     "e000df99" /* <- IuUP header */
+			     "160051673c01270000820000001710000100" /* IuUP params */),
+	       pdu_priv);
+
+#define RTP_HEADER "8060944c6256042c00010102"
+#define IUUP_HEADER "0100e2b3"
+#define RTP_PAYLOAD "6cfb23bc46d18180c3e5ffe040045600005a7d35b625b80005fff03214ced0"
+	printf("\nReceive payload encapsulated in IuUP. Expecting rx_payload() of just RTP packet\n");
+	printf("i.e. should strip away " IUUP_HEADER "\n");
+	expect_rx_payload = RTP_HEADER RTP_PAYLOAD;
+	rx_pdu(cn,
+	       msgb_from_hex("IuUP-Data",
+			     RTP_HEADER IUUP_HEADER RTP_PAYLOAD),
+	       pdu_priv);
+
+	printf("\nTransmit RTP. Expecting tx_msg() with inserted IuUP header\n");
+	expect_tx_msg = RTP_HEADER "000002b3" RTP_PAYLOAD;
+	tx_payload(cn,
+		   msgb_from_hex("RTP data", RTP_HEADER RTP_PAYLOAD),
+		   pdu_priv);
+
+	printf("\nMore RTP, each time the Frame Nr advances, causing a new header CRC.\n");
+	expect_tx_msg = RTP_HEADER "0100e2b3" RTP_PAYLOAD;
+	tx_payload(cn,
+		   msgb_from_hex("RTP data", RTP_HEADER RTP_PAYLOAD),
+		   pdu_priv);
+	expect_tx_msg = RTP_HEADER "02007eb3" RTP_PAYLOAD;
+	tx_payload(cn,
+		   msgb_from_hex("RTP data", RTP_HEADER RTP_PAYLOAD),
+		   pdu_priv);
+	expect_tx_msg = RTP_HEADER "03009eb3" RTP_PAYLOAD;
+	tx_payload(cn,
+		   msgb_from_hex("RTP data", RTP_HEADER RTP_PAYLOAD),
+		   pdu_priv);
+
+	printf("All done.\n");
+}
+
+static const struct log_info_cat log_categories[] = {
+};
+
+const struct log_info log_info = {
+	.cat = log_categories,
+	.num_cat = ARRAY_SIZE(log_categories),
+};
+
+int main(void)
+{
+	ctx = talloc_named_const(NULL, 0, __FILE__);
+	void *msgb_ctx = msgb_talloc_ctx_init(ctx, 0);
+	osmo_init_logging2(ctx, &log_info);
+
+	test_cn_session();
+
+	talloc_free(msgb_ctx);
+	return 0;
+}