diff --git a/src/Makefile.am b/src/Makefile.am
index ffde103..4022d4a 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -56,6 +56,7 @@ whttrackrundir = $(bindir)
 whttrackrun_SCRIPTS = webhttrack
 
 libhttrack_la_SOURCES =  htscore.c htsparse.c htsback.c htscache.c \
+	htscache_selftest.c \
 	htscatchurl.c htsfilters.c htsftp.c htshash.c coucal/coucal.c \
 	htshelp.c htslib.c htscoremain.c \
 	htsname.c htsrobots.c htstools.c htswizard.c \
@@ -65,7 +66,7 @@ libhttrack_la_SOURCES =  htscore.c htsparse.c htsback.c htscache.c \
 	md5.c \
 	minizip/ioapi.c minizip/mztools.c minizip/unzip.c minizip/zip.c \
 	hts-indextmpl.h htsalias.h htsback.h htsbase.h htssafe.h \
-	htsbasenet.h htsbauth.h htscache.h htscatchurl.h  \
+	htsbasenet.h htsbauth.h htscache.h htscache_selftest.h htscatchurl.h  \
 	htsconfig.h htscore.h htsparse.h htscoremain.h htsdefines.h  \
 	htsfilters.h htsftp.h htsglobal.h htshash.h coucal/coucal.h \
 	htshelp.h htsindex.h htslib.h htsmd5.h \
diff --git a/src/htscache_selftest.c b/src/htscache_selftest.c
new file mode 100644
index 0000000..c1a7eea
--- /dev/null
+++ b/src/htscache_selftest.c
@@ -0,0 +1,374 @@
+/* ------------------------------------------------------------ */
+/*
+HTTrack Website Copier, Offline Browser for Windows and Unix
+Copyright (C) 1998-2017 Xavier Roche and other contributors
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+Important notes:
+
+- We hereby ask people using this source NOT to use it in purpose of grabbing
+emails addresses, or collecting any other private information on persons.
+This would disgrace our work, and spoil the many hours we spent on it.
+
+Please visit our Website: http://www.httrack.com
+*/
+
+/* ------------------------------------------------------------ */
+/* File: htscache_selftest.c subroutines:                       */
+/*       in-process self-test for the (ZIP) cache subsystem      */
+/* Author: Xavier Roche                                         */
+/* ------------------------------------------------------------ */
+
+/* Drives the public cache API (cache_init / cache_add / cache_readex)
+   through a create -> read -> update cycle on a real on-disk ZIP cache,
+   asserting every header field and the (binary-safe) body round-trips.
+   Besides a few hand-crafted edge cases it stores a few thousand entries
+   (index/lookup scale) and a handful of large compressible/incompressible
+   bodies (zlib deflate/inflate). Reached via `httrack -#A <dir>`. */
+
+#define HTS_INTERNAL_BYTECODE
+
+#include "htscache_selftest.h"
+
+#include "htscache.h"
+#include "htscore.h"
+#include "htslib.h"
+#include "htszlib.h"
+
+#include <stdio.h>
+#include <string.h>
+
+#define SELFTEST_VOLUME 3000 /* number of small entries in the scale pass */
+
+/* Open a cache session. A write session (ro=0) rotates new.zip -> old.zip and
+   opens a fresh new.zip; a read session (ro=1) opens new.zip in place. */
+static void selftest_open(cache_back *cache, httrackp *opt, int ro) {
+  memset(cache, 0, sizeof(*cache));
+  cache->type = 1;
+  cache->log = stderr;
+  cache->errlog = stderr;
+  cache->hashtable = coucal_new(0);
+  cache->ro = ro;
+  cache_init(cache, opt);
+}
+
+static void selftest_open_for_write(cache_back *cache, httrackp *opt) {
+  selftest_open(cache, opt, 0);
+}
+
+static void selftest_open_for_read(cache_back *cache, httrackp *opt) {
+  selftest_open(cache, opt, 1);
+}
+
+static void selftest_close(cache_back *cache) {
+  if (cache->dat != NULL) {
+    fclose(cache->dat);
+    cache->dat = NULL;
+  }
+  if (cache->ndx != NULL) {
+    fclose(cache->ndx);
+    cache->ndx = NULL;
+  }
+  if (cache->zipOutput != NULL) {
+    zipClose(cache->zipOutput,
+             "Created by HTTrack Website Copier (cache self-test)");
+    cache->zipOutput = NULL;
+  }
+  if (cache->zipInput != NULL) {
+    unzClose(cache->zipInput);
+    cache->zipInput = NULL;
+  }
+  /* hashtable is intentionally not coucal_delete()d: it would dump a stats
+     summary to stderr on every call, and this is a one-shot CLI subcommand
+     that exits right after (same choice as the other -# cache subcommands) */
+}
+
+/* Store one entry. The body is copied into a private buffer (any size), so
+   callers may pass const data and cache_add never sees a cast-away qualifier;
+   it consumes everything synchronously, so the copy is freed on return. */
+static void store_entry(httrackp *opt, cache_back *cache, const char *adr,
+                        const char *fil, const char *save, int statuscode,
+                        const char *msg, const char *contenttype,
+                        const char *charset, const char *lastmodified,
+                        const char *etag, const char *location,
+                        const char *body, size_t body_len) {
+  htsblk r;
+  char locbuf[HTS_URLMAXSIZE * 2];
+  char *bodycopy = NULL;
+
+  hts_init_htsblk(&r);
+  r.statuscode = statuscode;
+  r.size = (LLint) body_len;
+  strcpybuff(r.msg, msg);
+  strcpybuff(r.contenttype, contenttype);
+  strcpybuff(r.charset, charset);
+  strcpybuff(r.lastmodified, lastmodified);
+  strcpybuff(r.etag, etag);
+  strcpybuff(locbuf, location);
+  r.location = locbuf;
+  r.is_write = 0;
+  /* an empty body must be a NULL pointer: cache_add rejects a non-NULL
+     pointer with size 0 */
+  if (body_len != 0) {
+    bodycopy = malloct(body_len);
+    memcpy(bodycopy, body, body_len);
+    r.adr = bodycopy;
+  }
+  /* all_in_cache=1: keep the body in the ZIP whatever the content-type,
+     so the read path never depends on a file on disk */
+  cache_add(opt, cache, &r, adr, fil, save, 1, NULL);
+  if (bodycopy != NULL) {
+    freet(bodycopy);
+  }
+}
+
+/* Read one entry back and check every field. Returns the number of
+   mismatches (0 == success). */
+static int check_entry(httrackp *opt, cache_back *cache, const char *adr,
+                       const char *fil, int statuscode, const char *msg,
+                       const char *contenttype, const char *charset,
+                       const char *lastmodified, const char *etag,
+                       const char *location, const char *body,
+                       size_t body_len) {
+  int fail = 0;
+  char *locbuf = malloct(HTS_URLMAXSIZE * 2);
+  htsblk r;
+
+  locbuf[0] = '\0';
+  /* readonly=1: pure read, no rename/disk-write decision logic */
+  r = cache_readex(opt, cache, adr, fil, "", locbuf, NULL, 1);
+
+#define CHECK_STR(field, want)                                                 \
+  do {                                                                         \
+    if (strcmp((field), (want)) != 0) {                                        \
+      fprintf(stderr,                                                          \
+              "cache-selftest: %s%s: " #field " is '%s', expected '%s'\n",     \
+              adr, fil, (field), (want));                                      \
+      fail++;                                                                  \
+    }                                                                          \
+  } while (0)
+
+  if (r.statuscode != statuscode) {
+    fprintf(stderr, "cache-selftest: %s%s: statuscode is %d, expected %d\n",
+            adr, fil, r.statuscode, statuscode);
+    fail++;
+  }
+  CHECK_STR(r.msg, msg);
+  CHECK_STR(r.contenttype, contenttype);
+  CHECK_STR(r.charset, charset);
+  CHECK_STR(r.lastmodified, lastmodified);
+  CHECK_STR(r.etag, etag);
+  CHECK_STR(locbuf, location);
+
+  if (r.size != (LLint) body_len) {
+    fprintf(stderr, "cache-selftest: %s%s: size is " LLintP ", expected %d\n",
+            adr, fil, (LLint) r.size, (int) body_len);
+    fail++;
+  } else if (body_len != 0 &&
+             (r.adr == NULL || memcmp(r.adr, body, body_len) != 0)) {
+    fprintf(stderr, "cache-selftest: %s%s: body mismatch\n", adr, fil);
+    fail++;
+  }
+
+#undef CHECK_STR
+
+  if (r.adr != NULL) {
+    freet(r.adr);
+  }
+  freet(locbuf);
+  return fail;
+}
+
+/* Fill a body of the requested size. kind 0 is highly compressible (a short
+   repeating pattern), kind 1 is incompressible (a deterministic PRNG), kind 2
+   alternates the two -- together they exercise both deflate outcomes. */
+static void gen_body(char *buf, size_t len, int kind) {
+  unsigned int seed = 0x9e3779b1u ^ (unsigned int) len;
+  size_t j;
+
+  for (j = 0; j < len; j++) {
+    if (kind == 0 || (kind == 2 && (j & 1) == 0)) {
+      buf[j] = (char) ('A' + (j % 26));
+    } else {
+      seed = seed * 1103515245u + 12345u;
+      buf[j] = (char) (seed >> 16);
+    }
+  }
+}
+
+int cache_selftests(httrackp *opt, const char *dir) {
+  int failures = 0;
+  cache_back cache;
+  int i;
+
+  /* near-limit field values. The etag stresses htsblk.etag[256]; the location
+     stresses a long redirect URL. Each cached header line is read back through
+     a HTS_URLMAXSIZE-sized parse buffer ("<field>: <value>\r\n"), so the
+     round-trippable value is shorter than HTS_URLMAXSIZE: 1000 stays safely
+     under that real limit. */
+  static char etag_long[251];
+  static char location_long[1001];
+
+  /* a body with embedded NUL and high bytes, to prove binary safety */
+  static const char binary_body[] = {
+      'P',  'N',  'G', '\0', '\r', '\n',        (char) 0xFF, (char) 0x80,
+      '\0', '\0', 'e', 'n',  'd',  (char) 0xCA, (char) 0xFE, '\n'};
+
+  /* large bodies for the compression pass; kept alive across the write and
+     read passes so the read can compare against them */
+  static const size_t large_size[] = {200000, 200000, 50000};
+  const int large_count = (int) (sizeof(large_size) / sizeof(large_size[0]));
+  char *large_body[3];
+
+  /* edge-case bodies, named so store and read assert the exact same bytes */
+  const char *const body_index = "<html><body>hello</body></html>";
+  const char *const body_api = "{\"k\":\"v\"}";
+  const char *const body_updated = "<html><body>UPDATED CONTENT</body></html>";
+  const char *const body_404 = "<html><body>404 Not Found</body></html>";
+
+  memset(etag_long, 'E', sizeof(etag_long) - 1);
+  etag_long[sizeof(etag_long) - 1] = '\0';
+  memset(location_long, 'L', sizeof(location_long) - 1);
+  location_long[sizeof(location_long) - 1] = '\0';
+
+  for (i = 0; i < large_count; i++) {
+    large_body[i] = malloct(large_size[i]);
+    gen_body(large_body[i], large_size[i], i);
+  }
+
+  /* set up an isolated cache directory */
+  {
+    char base[HTS_URLMAXSIZE];
+
+    strcpybuff(base, dir);
+    if (base[0] != '\0' && base[strlen(base) - 1] != '/') {
+      strcatbuff(base, "/");
+    }
+    StringCopy(opt->path_log, base);
+  }
+  opt->cache = 1;
+
+  /* pass 1: create everything in a single write session */
+  selftest_open_for_write(&cache, opt);
+
+  /* edge cases: normal HTML page */
+  store_entry(opt, &cache, "example.com", "/", "example.com/index.html", 200,
+              "OK", "text/html", "utf-8", "Mon, 01 Jan 2024 00:00:00 GMT",
+              "etag-normal", "", body_index, strlen(body_index));
+  /* redirect: empty body, empty optional fields, near-limit location */
+  store_entry(opt, &cache, "example.com", "/moved", "example.com/moved.html",
+              301, "Moved Permanently", "text/html", "", "", "", location_long,
+              NULL, 0);
+  /* non-HTML content-type kept in cache via all_in_cache, near-limit etag */
+  store_entry(opt, &cache, "example.com", "/api", "example.com/api.json", 200,
+              "OK", "application/json", "utf-8",
+              "Tue, 02 Jan 2024 12:00:00 GMT", etag_long, "", body_api,
+              strlen(body_api));
+  /* binary body */
+  store_entry(opt, &cache, "example.com", "/logo", "example.com/logo.png", 200,
+              "OK", "image/png", "", "", "etag-bin", "", binary_body,
+              sizeof(binary_body));
+  /* error status with a body and a location (non-2xx codes are cached too) */
+  store_entry(opt, &cache, "example.com", "/gone", "example.com/gone.html", 404,
+              "Not Found", "text/html", "utf-8", "", "etag-404",
+              "https://example.com/where-it-went", body_404, strlen(body_404));
+
+  /* scale: a few thousand small entries */
+  for (i = 0; i < SELFTEST_VOLUME; i++) {
+    char fil[64], save[128], body[64];
+
+    sprintf(fil, "/v/%05d", i);
+    sprintf(save, "example.com/v/%05d.html", i);
+    sprintf(body, "<html>volume entry %d</html>", i);
+    store_entry(opt, &cache, "example.com", fil, save, 200, "OK", "text/html",
+                "utf-8", "", "", "", body, strlen(body));
+  }
+
+  /* compression: a few large bodies */
+  for (i = 0; i < large_count; i++) {
+    char fil[64], save[128];
+
+    sprintf(fil, "/big/%d.bin", i);
+    sprintf(save, "example.com/big/%d.bin", i);
+    store_entry(opt, &cache, "example.com", fil, save, 200, "OK",
+                "application/octet-stream", "", "", "", "", large_body[i],
+                large_size[i]);
+  }
+
+  selftest_close(&cache);
+
+  /* pass 2: read back and verify everything round-tripped */
+  selftest_open_for_read(&cache, opt);
+
+  failures += check_entry(opt, &cache, "example.com", "/", 200, "OK",
+                          "text/html", "utf-8", "Mon, 01 Jan 2024 00:00:00 GMT",
+                          "etag-normal", "", body_index, strlen(body_index));
+  failures += check_entry(opt, &cache, "example.com", "/moved", 301,
+                          "Moved Permanently", "text/html", "", "", "",
+                          location_long, NULL, 0);
+  failures +=
+      check_entry(opt, &cache, "example.com", "/api", 200, "OK",
+                  "application/json", "utf-8", "Tue, 02 Jan 2024 12:00:00 GMT",
+                  etag_long, "", body_api, strlen(body_api));
+  failures +=
+      check_entry(opt, &cache, "example.com", "/logo", 200, "OK", "image/png",
+                  "", "", "etag-bin", "", binary_body, sizeof(binary_body));
+  failures += check_entry(opt, &cache, "example.com", "/gone", 404, "Not Found",
+                          "text/html", "utf-8", "", "etag-404",
+                          "https://example.com/where-it-went", body_404,
+                          strlen(body_404));
+
+  for (i = 0; i < SELFTEST_VOLUME; i++) {
+    char fil[64], body[64];
+
+    sprintf(fil, "/v/%05d", i);
+    sprintf(body, "<html>volume entry %d</html>", i);
+    failures +=
+        check_entry(opt, &cache, "example.com", fil, 200, "OK", "text/html",
+                    "utf-8", "", "", "", body, strlen(body));
+  }
+
+  for (i = 0; i < large_count; i++) {
+    char fil[64];
+
+    sprintf(fil, "/big/%d.bin", i);
+    failures += check_entry(opt, &cache, "example.com", fil, 200, "OK",
+                            "application/octet-stream", "", "", "", "",
+                            large_body[i], large_size[i]);
+  }
+
+  selftest_close(&cache);
+
+  /* pass 3: update one edge entry with new body and headers */
+  selftest_open_for_write(&cache, opt);
+  store_entry(opt, &cache, "example.com", "/", "example.com/index.html", 200,
+              "OK", "text/html", "iso-8859-1", "Wed, 03 Jan 2024 09:30:00 GMT",
+              "etag-updated", "", body_updated, strlen(body_updated));
+  selftest_close(&cache);
+
+  /* pass 4: re-read and confirm the updated value, not the old one */
+  selftest_open_for_read(&cache, opt);
+  failures +=
+      check_entry(opt, &cache, "example.com", "/", 200, "OK", "text/html",
+                  "iso-8859-1", "Wed, 03 Jan 2024 09:30:00 GMT", "etag-updated",
+                  "", body_updated, strlen(body_updated));
+  selftest_close(&cache);
+
+  for (i = 0; i < large_count; i++) {
+    freet(large_body[i]);
+  }
+
+  return failures;
+}
diff --git a/src/htscache_selftest.h b/src/htscache_selftest.h
new file mode 100644
index 0000000..c120eb0
--- /dev/null
+++ b/src/htscache_selftest.h
@@ -0,0 +1,49 @@
+/* ------------------------------------------------------------ */
+/*
+HTTrack Website Copier, Offline Browser for Windows and Unix
+Copyright (C) 1998-2017 Xavier Roche and other contributors
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+Important notes:
+
+- We hereby ask people using this source NOT to use it in purpose of grabbing
+emails addresses, or collecting any other private information on persons.
+This would disgrace our work, and spoil the many hours we spent on it.
+
+Please visit our Website: http://www.httrack.com
+*/
+
+/* ------------------------------------------------------------ */
+/* File: htscache_selftest.h                                    */
+/* Author: Xavier Roche                                         */
+/* ------------------------------------------------------------ */
+
+#ifndef HTSCACHE_SELFTEST_DEFH
+#define HTSCACHE_SELFTEST_DEFH
+
+#ifdef HTS_INTERNAL_BYTECODE
+
+#ifndef HTS_DEF_FWSTRUCT_httrackp
+#define HTS_DEF_FWSTRUCT_httrackp
+typedef struct httrackp httrackp;
+#endif
+
+/* Run the cache create/read/update self-test against a working directory.
+   Returns the number of failed checks (0 == success). */
+int cache_selftests(httrackp *opt, const char *dir);
+
+#endif
+
+#endif
diff --git a/src/htscoremain.c b/src/htscoremain.c
index 3cf3e48..fe911aa 100644
--- a/src/htscoremain.c
+++ b/src/htscoremain.c
@@ -46,6 +46,7 @@ Please visit our Website: http://www.httrack.com
 #include "htszlib.h"
 #include "htscharset.h"
 #include "htsencoding.h"
+#include "htscache_selftest.h"
 #include "htsmd5.h"
 
 #include <ctype.h>
@@ -2113,6 +2114,19 @@ static int hts_main_internal(int argc, char **argv, httrackp * opt) {
           case '#':{           // non documenté
               com++;
               switch (*com) {
+              case 'A': // cache self-test: httrack -#A <dir>
+                if (na + 1 < argc) {
+                  const int err = cache_selftests(opt, argv[na + 1]);
+
+                  printf("cache-selftest: %s\n", err ? "FAIL" : "OK");
+                  htsmain_free();
+                  return err;
+                } else {
+                  fprintf(stderr, "Option #A requires a directory argument\n");
+                  htsmain_free();
+                  return 1;
+                }
+                break;
               case 'C':        // list cache files : httrack -#C '*spid*.gif' will attempt to find the matching file
                 {
                   int hasFilter = 0;
diff --git a/tests/01_engine-cache.test b/tests/01_engine-cache.test
new file mode 100755
index 0000000..90d711f
--- /dev/null
+++ b/tests/01_engine-cache.test
@@ -0,0 +1,46 @@
+#!/bin/bash
+#
+
+# Cache create/read/update logic (driven by 'httrack -#A <dir>').
+#
+# The in-process self-test stores several hand-crafted edge entries (normal
+# HTML, an empty redirect with a near-limit location, a non-HTML body kept via
+# all-in-cache, a binary body with embedded NUL/high bytes), a few thousand
+# small entries (index/lookup scale), and a few large compressible and
+# incompressible bodies (zlib deflate/inflate). It reads everything back
+# asserting every header field and the body round-trip byte for byte, then
+# updates one entry and confirms the new value is read back. It exits non-zero
+# on the first mismatch.
+
+set -eu
+
+dir=$(mktemp -d)
+trap 'rm -rf "$dir"' EXIT
+
+# Like the other -# debug modes, a trailing token (the working directory) is
+# required; a bare '-#A' falls through to the usage screen.
+out=$(httrack -#A "$dir")
+
+# Match the exact success line, so the test cannot pass for an unrelated reason
+# (e.g. the -#A mode being gone and falling through to the usage screen, which
+# also exits non-zero but never prints this).
+test "$out" = "cache-selftest: OK" || {
+    echo "expected 'cache-selftest: OK', got: $out" >&2
+    exit 1
+}
+
+# The self-test must have actually produced a ZIP cache on disk.
+test -e "$dir/hts-cache/new.zip" || {
+    echo "no ZIP cache was written by the self-test" >&2
+    exit 1
+}
+
+# Sanity-check the cache footprint: the few-thousand-entry pass is expected to
+# weigh ~1-2 MB. Fail if it balloons well past that (e.g. a per-entry overhead
+# regression or runaway growth), so the cache size stays bounded.
+ceiling=$((4 * 1024 * 1024))
+bytes=$(du -sb "$dir/hts-cache" | cut -f1)
+test "$bytes" -le "$ceiling" || {
+    echo "cache footprint $bytes bytes exceeds ${ceiling} ceiling" >&2
+    exit 1
+}
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 5c1dbb3..fc08fee 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -11,6 +11,7 @@ TESTS_ENVIRONMENT += top_srcdir=$(top_srcdir)
 TEST_EXTENSIONS = .test
 TESTS = \
 	00_runnable.test \
+	01_engine-cache.test \
 	01_engine-charset.test \
 	01_engine-cmdline.test \
 	01_engine-entities.test \