diff --git a/tests/Makefile.am b/tests/Makefile.am
index 63c8b7ae..8ea3a3ef 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -646,7 +646,7 @@ test_memory_pool_and_config_SOURCES = test_memory_pool_and_config.c
 test_memory_pool_and_config_CFLAGS = -I$(top_srcdir)/src -I$(top_srcdir)/lib
 test_memory_pool_and_config_LDADD = $(COMMON_LIBS)
 
-test_packet_dump_SOURCES = test_packet_dump.c
+test_packet_dump_SOURCES = test_packet_dump.c ../src/transport_layer/packet_dump.c
 test_packet_dump_CFLAGS = -I$(top_srcdir)/src -I$(top_srcdir)/lib
 test_packet_dump_LDADD = $(COMMON_LIBS)
 
diff --git a/tests/test_packet_dump.c b/tests/test_packet_dump.c
index 139cd0d1..9987c64d 100644
--- a/tests/test_packet_dump.c
+++ b/tests/test_packet_dump.c
@@ -1,26 +1,182 @@
+/* Проверки ограничений входа и диагностического вывода настоящего IPv4-форматтера. */
 #include <stdio.h>
-#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
 #include "../lib/debug_config.h"
+#include "../lib/mem.h"
+#include "../src/transport_layer/packet_dump.h"
 
-// Simple test packet dump
-void test_packet_dump() {
-    uint8_t test_data[] = {0x02, 0x11, 0x22, 0x33, 0x44, 0x55};
-    
-    // Simulate single-line packet dump
-    char hex_buf[32];
-    snprintf(hex_buf, sizeof(hex_buf), "%02x%02x%02x%02x%02x%02x", 
-             test_data[0], test_data[1], test_data[2], test_data[3], test_data[4], test_data[5]);
-    
-    DEBUG_INFO(DEBUG_CATEGORY_ETCP, "TEST_SEND: len=%zu hex=%s", sizeof(test_data), hex_buf);
-    DEBUG_INFO(DEBUG_CATEGORY_ETCP, "TEST_COMPACT: link=NULL type=0x%02x ts=0 len=%zu", test_data[0], sizeof(test_data));
+#define CHECK(expr) do { \
+    if (!(expr)) { DEBUG_ERROR(DEBUG_CATEGORY_SYS, "packet dump test line=%d: %s", __LINE__, #expr); exit(1); } \
+} while (0)
+
+static void expect_contains(const char* text, const char* part) {
+    if (!strstr(text, part)) {
+        DEBUG_ERROR(DEBUG_CATEGORY_SYS, "packet dump: missing '%s' in '%s'", part, text);
+        exit(1);
+    }
 }
 
-int main() {
-    debug_config_init();
-    debug_set_level(DEBUG_LEVEL_TRACE);
-    debug_set_categories(DEBUG_CATEGORY_ALL);
-    
-    DEBUG_INFO(DEBUG_CATEGORY_ETCP, "=== Testing single-line packet dump ===");
-    test_packet_dump();
+static void init_packet(uint8_t* packet, size_t total, unsigned ihl, uint8_t protocol) {
+    memset(packet, 0, total);
+    packet[0] = 0x40 | (ihl / 4);
+    packet[2] = (uint8_t)(total >> 8); packet[3] = (uint8_t)total;
+    packet[9] = protocol;
+    packet[12] = 192; packet[13] = 168; packet[14] = 1; packet[15] = 2;
+    packet[16] = 10; packet[17] = 20; packet[18] = 30; packet[19] = 40;
+}
+
+static void test_protocols(void) {
+    uint8_t packet[60];
+    init_packet(packet, 40, 20, 6);
+    packet[22] = 0xff; packet[23] = 0xff;
+    packet[24] = 0x89; packet[25] = 0xab; packet[26] = 0xcd; packet[27] = 0xef;
+    packet[28] = 0xff; packet[29] = 0xff; packet[30] = 0xff; packet[31] = 0xff;
+    packet[32] = 0x50; packet[33] = 0xff; packet[34] = 0x80; packet[35] = 0x01;
+    const char* out = dump_ip_packet_to_buffer(packet, 40);
+    CHECK(strcmp(out, "IPv4 TCP 192.168.1.2:0 -> 10.20.30.40:65535 (40 bytes) "
+                      "[FIN,SYN,RST,PSH,ACK,URG,ECE,CWR] seq=2309737967 ack=4294967295 win=32769 "
+                      "data: 0000ffff89abcdef ffffffff50ff8001 00000000") == 0);
+    DEBUG_INFO(DEBUG_CATEGORY_SYS, "%s", out);
+    packet[33] = 0;
+    expect_contains(dump_ip_packet_to_buffer(packet, 40), "[none]");
+
+    init_packet(packet, 28, 20, 17);
+    packet[22] = 0x01; packet[23] = 0xbb; packet[25] = 8;
+    CHECK(strcmp(dump_ip_packet_to_buffer(packet, 28),
+                 "IPv4 UDP 192.168.1.2:0 -> 10.20.30.40:443 (28 bytes) len=8 data: 000001bb00080000") == 0);
+
+    init_packet(packet, 28, 20, 1);
+    packet[20] = 8; packet[24] = 0x12; packet[25] = 0x34; packet[26] = 0xab; packet[27] = 0xcd;
+    expect_contains(dump_ip_packet_to_buffer(packet, 28), "echo_request seq=43981 id=4660 data: 080000001234abcd");
+    packet[20] = 0;
+    expect_contains(dump_ip_packet_to_buffer(packet, 28), "echo_reply seq=43981 id=4660");
+    packet[20] = 3; packet[21] = 1;
+    expect_contains(dump_ip_packet_to_buffer(packet, 28), "type=3 code=1");
+
+    init_packet(packet, 20, 20, 99);
+    CHECK(strcmp(dump_ip_packet_to_buffer(packet, 20),
+                 "IPv4 UNKNOWN 192.168.1.2 -> 10.20.30.40 (20 bytes) data: ") == 0);
+    DEBUG_INFO(DEBUG_CATEGORY_SYS, "PASS protocols: TCP flags/none, zero/max ports, seq/ack/window, UDP, ICMP, unknown/empty");
+}
+
+static void test_input_diagnostics(void) {
+    uint8_t packet[60];
+    expect_contains(dump_ip_packet_to_buffer(NULL, 0), "Missing IP packet");
+    expect_contains(dump_ip_packet_to_buffer(NULL, 100), "Missing IP packet");
+    init_packet(packet, 20, 20, 99);
+    packet[0] = 0x65;
+    expect_contains(dump_ip_packet_to_buffer(packet, 20), "Non-IPv4 packet: version=6");
+    for (unsigned ihl = 0; ihl < 5; ihl++) {
+        packet[0] = 0x40 | ihl;
+        expect_contains(dump_ip_packet_to_buffer(packet, 20), "Invalid IP header length");
+    }
+    init_packet(packet, 20, 20, 99);
+    packet[3] = 19;
+    expect_contains(dump_ip_packet_to_buffer(packet, 20), "Invalid IP total length");
+    packet[3] = 0;
+    expect_contains(dump_ip_packet_to_buffer(packet, 20), "Invalid IP total length");
+    packet[0] = 0x4f;
+    expect_contains(dump_ip_packet_to_buffer(packet, 20), "Truncated IP header");
+    DEBUG_INFO(DEBUG_CATEGORY_SYS, "PASS input diagnostics: NULL, version, invalid IHL, total length, missing options");
+}
+
+static void test_lengths_and_alignment(void) {
+    uint8_t packet[76];
+    init_packet(packet, sizeof(packet), 60, 17);
+    packet[65] = 16;
+    debug_set_category_level(DEBUG_CATEGORY_DUMP, DEBUG_LEVEL_DISABLED);
+    for (size_t len = 0; len <= sizeof(packet); len++) {
+        uint8_t* exact = u_malloc(len + 1);
+        CHECK(exact != NULL);
+        memcpy(exact + 1, packet, len);
+        const char* out = dump_ip_packet_to_buffer(exact + 1, len);
+        if (len < 20) expect_contains(out, "Packet too small");
+        else if (len < 60) expect_contains(out, "Truncated IP header");
+        else if (len < sizeof(packet)) expect_contains(out, "Truncated IPv4 packet");
+        else expect_contains(out, "UDP 192.168.1.2:0 -> 10.20.30.40:0 (76 bytes) len=16");
+        CHECK(memcmp(exact + 1, packet, len) == 0);
+        u_free(exact);
+    }
+    debug_set_category_level(DEBUG_CATEGORY_DUMP, DEBUG_LEVEL_WARN);
+
+    init_packet(packet, 28, 20, 17);
+    packet[25] = 8;
+    memset(packet + 28, 0xab, sizeof(packet) - 28);
+    const char* out = dump_ip_packet_to_buffer(packet, sizeof(packet));
+    expect_contains(out, "(28 bytes) len=8 data: 0000000000080000");
+    CHECK(!strstr(out, "abab"));
+    DEBUG_INFO(DEBUG_CATEGORY_SYS, "PASS lengths: 77 capture lengths, IP options, unaligned input, ignored capture suffix, unchanged input");
+}
+
+static void test_fragments(void) {
+    uint8_t packet[40];
+    const uint8_t protocols[] = {6, 17, 1};
+    for (size_t i = 0; i < sizeof(protocols); i++) {
+        init_packet(packet, sizeof(packet), 20, protocols[i]);
+        packet[7] = 1;
+        const char* out = dump_ip_packet_to_buffer(packet, sizeof(packet));
+        expect_contains(out, "192.168.1.2 -> 10.20.30.40 (40 bytes) fragment offset=8 MF=0");
+        CHECK(!strstr(out, "seq=") && !strstr(out, "len=") && !strstr(out, "type=") && !strstr(out, "header:"));
+        packet[6] = 0x3f; packet[7] = 0xff;
+        expect_contains(dump_ip_packet_to_buffer(packet, sizeof(packet)), "fragment offset=65528 MF=1");
+    }
+    init_packet(packet, sizeof(packet), 20, 6);
+    packet[6] = 0x20; packet[32] = 0x50;
+    expect_contains(dump_ip_packet_to_buffer(packet, sizeof(packet)), "[none] seq=0 ack=0 win=0 fragment offset=0 MF=1");
+    packet[3] = 28;
+    expect_contains(dump_ip_packet_to_buffer(packet, 28), "partial header: available=8 required=20 fragment offset=0 MF=1");
+    packet[6] = 0;
+    expect_contains(dump_ip_packet_to_buffer(packet, 28), "truncated header: available=8 required=20");
+    DEBUG_INFO(DEBUG_CATEGORY_SYS, "PASS fragments: subsequent/first, MF, maximum offset, partial transport header");
+}
+
+static void test_hex_bounds(void) {
+    const uint8_t protocols[] = {6, 17, 1, 99};
+    size_t cases = 0;
+    debug_set_category_level(DEBUG_CATEGORY_DUMP, DEBUG_LEVEL_DISABLED);
+    for (size_t p = 0; p < sizeof(protocols); p++) {
+        for (unsigned ihl = 20; ihl <= 60; ihl += 4) {
+            for (size_t count = 0; count <= 65; count++) {
+                size_t total = ihl + count;
+                uint8_t* exact = u_malloc(total + 1);
+                CHECK(exact != NULL);
+                uint8_t* packet = exact + 1;
+                init_packet(packet, total, ihl, protocols[p]);
+                memset(packet + ihl, 0xa5, count);
+                const char* out = dump_ip_packet_to_buffer(packet, total);
+                const char* hex = strstr(out, " data: ");
+                CHECK(hex != NULL && strlen(out) < 1024);
+                hex += strlen(" data: ");
+                size_t displayed = count < 32 ? count : 32;
+                CHECK(strlen(hex) == displayed * 2 + (displayed ? (displayed - 1) / 8 : 0));
+                for (size_t i = 0; i < displayed; i++) {
+                    if (i && i % 8 == 0) CHECK(*hex++ == ' ');
+                    CHECK(*hex++ == 'a'); CHECK(*hex++ == '5');
+                }
+                CHECK(*hex == '\0');
+                u_free(exact);
+                cases++;
+            }
+        }
+    }
+    debug_set_category_level(DEBUG_CATEGORY_DUMP, DEBUG_LEVEL_WARN);
+    DEBUG_INFO(DEBUG_CATEGORY_SYS, "PASS hex bounds: %zu cases, four protocols, 11 IHL values, 0..65 payload bytes", cases);
+}
+
+int main(void) {
+    debug_config_init(); debug_set_level(DEBUG_LEVEL_INFO);
+    debug_set_category_level(DEBUG_CATEGORY_DUMP, DEBUG_LEVEL_WARN);
+    test_protocols();
+    test_input_diagnostics();
+    test_lengths_and_alignment();
+    test_fragments();
+    test_hex_bounds();
+    uint8_t packet[20];
+    init_packet(packet, sizeof(packet), 20, 99);
+    char* first = dump_ip_packet_to_buffer(packet, sizeof(packet));
+    CHECK(first == dump_ip_packet_to_buffer(NULL, 0));
+    expect_contains(first, "Missing IP packet");
+    DEBUG_INFO(DEBUG_CATEGORY_SYS, "PASS packet dump: 5 groups and static output lifetime");
     return 0;
 }