diff --git a/tests/Makefile.am b/tests/Makefile.am
index c9187e45..e1f4ba5f 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -83,6 +83,7 @@ check_PROGRAMS = \
 	test_dm_e2e \
 	test_dm_media \
 	test_dm_worker \
+	test_attachment \
 	test_call \
 	test_call_headless \
 	test_radio \
@@ -191,6 +192,8 @@ test_reality_config_CFLAGS = -I$(top_srcdir)/src -I$(top_srcdir)/src/transport_l
 test_reality_config_LDADD = $(LIBUTUN) $(CRYPTO_LIBS) $(COMMON_LIBS)
 
 test_dm_SOURCES = test_dm.c
+test_attachment_SOURCES = test_attachment.c
+test_attachment_LDADD = $(LIBUTUN) $(CRYPTO_LIBS) $(COMMON_LIBS)
 test_dm_CFLAGS = -I$(top_srcdir)/src -I$(top_srcdir)/src/transport_layer -I$(top_srcdir)/lib
 test_dm_LDADD = $(LIBUTUN) $(CRYPTO_LIBS) $(COMMON_LIBS)
 
diff --git a/tests/test_dm_worker.c b/tests/test_dm_worker.c
index b9c28486..4f08d7b8 100644
--- a/tests/test_dm_worker.c
+++ b/tests/test_dm_worker.c
@@ -82,6 +82,13 @@ static void heartbeat(void* arg) {
     if (!t->heartbeat) { DEBUG_ERROR(DEBUG_CATEGORY_DM, "heartbeat allocation failed"); uasync_stop(t->ua); }
 }
 
+struct cancellation_test { int worked, calls, error; };
+static void cancellation_work(void* arg) { ((struct cancellation_test*)arg)->worked = 1; }
+static void cancellation_done(void* arg, int error) {
+    struct cancellation_test* test = arg;
+    test->calls++; test->error = error;
+}
+
 int main(void) {
     debug_config_init(); debug_set_level(DEBUG_LEVEL_ERROR);
     struct worker_test t = {0};
@@ -93,7 +100,14 @@ int main(void) {
     if (!t.completed) uasync_mainloop(t.ua);
     if (t.heartbeat) uasync_cancel_timeout(t.ua, t.heartbeat);
     int ok = t.completed && !t.result && t.beats >= 10;
-    media_async_destroy(t.ma); uasync_destroy(t.ua, 0);
+    media_async_destroy(t.ma);
+    struct cancellation_test cancellation = {0};
+    t.ma = media_async_create();
+    media_async_submit(t.ma, t.ua, cancellation_work, &cancellation, cancellation_done, &cancellation);
+    media_async_destroy(t.ma); /* Join worker и отмена уже posted completion до poll. */
+    uasync_poll(t.ua, 0);
+    ok = ok && cancellation.worked && cancellation.calls == 1 && cancellation.error == MEDIA_ASYNC_CANCELLED;
+    uasync_destroy(t.ua, 0);
     printf("test_dm_worker: 8MiB encrypt/decrypt, runs=%u heartbeat=%u max_gap=%.1fms %s\n",
            t.encryptions, t.beats, t.max_gap / 10.0, ok ? "PASS" : "FAIL");
     return !ok;