diff --git a/tests/test_etcp_ping.c b/tests/test_etcp_ping.c
new file mode 100644
index 00000000..7c4e563a
--- /dev/null
+++ b/tests/test_etcp_ping.c
@@ -0,0 +1,107 @@
+// test_etcp_ping.c - unit test for etcp_send_ping with callback on PONG/timeout
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdint.h>
+#include "../src/etcp_connections.h"
+#include "../src/utun_instance.h"
+#include "../lib/u_async.h"
+#include "../lib/debug_config.h"
+#include "../lib/mem.h"
+#include "../src/secure_channel.h"
+
+#define TEST_TIMEOUT_MS 500
+static int test_completed = 0;
+static int cb_called = 0;
+static int cb_success = -1;
+static uint64_t test_nonce = 0;
+
+static void ping_test_callback(int success, void* arg, uint64_t nonce) {
+    (void)arg;
+    cb_called++;
+    cb_success = success;
+    test_nonce = nonce;
+    DEBUG_INFO(DEBUG_CATEGORY_ETCP, "ping_test_callback: success=%d nonce=%016llx", success, (unsigned long long)nonce);
+    test_completed = 1;
+}
+
+int main(void) {
+    debug_config_init();
+    debug_set_level(DEBUG_LEVEL_TRACE);
+    debug_set_categories(DEBUG_CATEGORY_ALL);
+    
+    DEBUG_INFO(DEBUG_CATEGORY_ETCP, "=== ETCP Ping Test ===");
+    
+    struct UASYNC* ua = uasync_create();
+    if (!ua) {
+        DEBUG_ERROR(DEBUG_CATEGORY_ETCP, "uasync_create failed");
+        return 1;
+    }
+    
+    struct UTUN_INSTANCE* instance = u_calloc(1, sizeof(struct UTUN_INSTANCE));
+    if (!instance) {
+        DEBUG_ERROR(DEBUG_CATEGORY_ETCP, "instance alloc failed");
+        uasync_destroy(ua, 0);
+        return 1;
+    }
+    instance->ua = ua;
+    instance->node_id = 0x1234567890ABCDEFULL;
+    // dummy keys for test (full init in production)
+    for (int i = 0; i < SC_PRIVKEY_SIZE; i++) {
+        instance->my_keys.private_key[i] = i;
+        instance->my_keys.public_key[i] = i + 64;
+    }
+    
+    struct ETCP_SOCKET* dummy_sock = u_calloc(1, sizeof(struct ETCP_SOCKET));
+    if (!dummy_sock) {
+        DEBUG_ERROR(DEBUG_CATEGORY_ETCP, "dummy sock alloc failed");
+        utun_instance_destroy(instance);
+        uasync_destroy(ua, 0);
+        return 1;
+    }
+    dummy_sock->instance = instance;
+    dummy_sock->fd = socket(AF_INET, SOCK_DGRAM, 0);
+    dummy_sock->local_addr.ss_family = AF_INET;
+    instance->etcp_sockets = dummy_sock;
+    
+    // dummy pubkey
+    uint8_t dummy_pubkey[SC_PUBKEY_SIZE];
+    for (int i = 0; i < SC_PUBKEY_SIZE; i++) dummy_pubkey[i] = i;
+    
+    struct sockaddr_storage test_addr;
+    memset(&test_addr, 0, sizeof(test_addr));
+    struct sockaddr_in* sin = (struct sockaddr_in*)&test_addr;
+    sin->sin_family = AF_INET;
+    sin->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
+    sin->sin_port = htons(12345);
+    
+    // test timeout path (no receiver, expect success=0)
+    int ret = etcp_send_ping(instance, dummy_pubkey, &test_addr, 100, ping_test_callback, NULL);
+    if (ret != 0) {
+        DEBUG_ERROR(DEBUG_CATEGORY_ETCP, "etcp_send_ping failed ret=%d", ret);
+        utun_instance_destroy(instance);
+        uasync_destroy(ua, 0);
+        return 1;
+    }
+    
+    // run uasync to trigger timeout cb
+    for (int i = 0; i < 20 && !test_completed; i++) {
+        uasync_poll(ua, 50);
+    }
+    
+    if (cb_called != 1 || cb_success != 0) {
+        DEBUG_ERROR(DEBUG_CATEGORY_ETCP, "callback not triggered correctly: called=%d success=%d", cb_called, cb_success);
+        utun_instance_destroy(instance);
+        uasync_destroy(ua, 0);
+        return 1;
+    }
+    
+    DEBUG_INFO(DEBUG_CATEGORY_ETCP, "Ping timeout test PASSED (cb called with success=0)");
+    
+    // cleanup
+    utun_instance_destroy(instance);
+    uasync_destroy(ua, 0);
+    
+    DEBUG_INFO(DEBUG_CATEGORY_ETCP, "ETCP ping unit test PASSED");
+    return 0;
+}