test(functests): migration/MUC/timestamp tests, group rebalancing

Add 11 new export/import tests (24 → 35): 4 MUC database, 3 timestamp
verification, 3 migration stress, 1 LMC correction with negative assert.

Add delay-stamp timestamp checks to 5 base tests via /time chat set
iso8601 and /history on (previously passed by accident from PTY buffer).

Replace magic numbers: NEGATIVE_ASSERT_TIMEOUT, MIN_ELAPSED_INIT.
Add per-test slow/fast thresholds and TZ override (prof_test_tz).

Rebalance groups by whole logical blocks (spread 46s → 3s):
G1=52s G2=50s G3=53s G4=53s. All 129 tests pass.

tests/functionaltests/functionaltests.c

@@ -14,11 +14,11 @@
  * flaky tests caused by leftover state. The overhead is acceptable since
  * functional tests run less frequently than unit tests.
  *
- * Tests are organized into groups for better maintainability and parallel execution:
- *   Group 1: Connect, Ping, Rooms, Software, Last Activity, Autoping, Disco
- *   Group 2: Message, Receipts, Roster, Export/Import (+SQLite)
- *   Group 3: Presence, Disconnect, DB History
- *   Group 4: Chat Session, MUC, Carbons
+ * Tests are organized into groups balanced for parallel execution:
+ *   Group 1: Connect, Ping, Rooms, Software, Last Activity, Autoping, Disco, Roster
+ *   Group 2: Export/Import (core + bidirectional), Receipts
+ *   Group 3: Presence, Disconnect, DB History, Message, MUC Database
+ *   Group 4: Chat Session, MUC, Carbons, Migration Stress
  *
  * Parallel execution:
  *   ./functionaltests        - run all tests sequentially
@@ -61,7 +61,19 @@
 #endif
 
 /* Macro to wrap each test with setup/teardown functions */
-#define PROF_FUNC_TEST(test) cmocka_unit_test_setup_teardown(test, init_prof_test, close_prof_test)
+#define PROF_FUNC_TEST(test) { #test, test, init_prof_test, close_prof_test, #test }
+
+#ifdef HAVE_SQLITE
+/* Custom init that sets a non-UTC timezone (POSIX TST-3 = UTC+3) */
+static int
+init_tz_plus3_test(void** state)
+{
+    prof_test_tz = "TST-3";
+    int ret = init_prof_test(state);
+    prof_test_tz = "UTC";
+    return ret;
+}
+#endif
 
 int
 main(int argc, char* argv[])
@@ -83,8 +95,8 @@ main(int argc, char* argv[])
     fprintf(stderr, "[PROF_TEST] Starting functional tests, group=%d\n", group);
 
     /* ============================================================
-     * GROUP 1: Connect, Ping, Rooms, Software, Last Activity, Disco
-     * Basic XMPP session establishment and server queries
+     * GROUP 1: Connect, Ping, Rooms, Software, Last Activity, Disco, Roster
+     * Basic XMPP session establishment, server queries, contact mgmt
      * ============================================================ */
     const struct CMUnitTest group1_tests[] = {
         /* Connection tests - verify login, roster, bookmarks */
@@ -141,11 +153,18 @@ main(int argc, char* argv[])
         PROF_FUNC_TEST(disco_info_without_name),
         PROF_FUNC_TEST(disco_items_without_name),
         PROF_FUNC_TEST(disco_info_service_unavailable),
+
+        /* Roster management - add/remove/rename contacts */
+        PROF_FUNC_TEST(sends_new_item),
+        PROF_FUNC_TEST(sends_new_item_nick),
+        PROF_FUNC_TEST(sends_remove_item),
+        PROF_FUNC_TEST(sends_remove_item_nick),
+        PROF_FUNC_TEST(sends_nick_change),
     };
 
     /* ============================================================
-     * GROUP 2: Message, Receipts, Roster, Export/Import
-     * Core messaging and contact management
+     * GROUP 2: Export/Import (core + bidirectional), Receipts
+     * Cross-backend migration, message timestamp round-trip
      * ============================================================ */
     const struct CMUnitTest group2_tests[] = {
 #ifdef HAVE_SQLITE
@@ -160,29 +179,26 @@ main(int argc, char* argv[])
         PROF_FUNC_TEST(verify_after_export),
         PROF_FUNC_TEST(switch_backends_independent_messages),
         PROF_FUNC_TEST(export_empty_contact),
-#endif
 
-        /* Basic message send/receive */
-        PROF_FUNC_TEST(message_send),
-        PROF_FUNC_TEST(message_receive_console),
-        PROF_FUNC_TEST(message_receive_chatwin),
+        /* Bidirectional migration — split timelines merged across backends */
+        PROF_FUNC_TEST(bidirectional_merge_to_flatfile),
+        PROF_FUNC_TEST(bidirectional_merge_to_sqlite),
+        PROF_FUNC_TEST(migration_incremental_accumulation),
+        PROF_FUNC_TEST(roundtrip_full_cycle),
+        PROF_FUNC_TEST(export_timestamps_preserved),
+        PROF_FUNC_TEST(import_timestamps_preserved),
+        { "export_timestamps_non_utc", export_timestamps_non_utc, init_tz_plus3_test, close_prof_test, "export_timestamps_non_utc" },
+#endif
 
         /* Message receipts - XEP-0184 */
         PROF_FUNC_TEST(does_not_send_receipt_request_to_barejid),
         PROF_FUNC_TEST(send_receipt_request),
         PROF_FUNC_TEST(send_receipt_on_request),
-
-        /* Roster management - add/remove/rename contacts */
-        PROF_FUNC_TEST(sends_new_item),
-        PROF_FUNC_TEST(sends_new_item_nick),
-        PROF_FUNC_TEST(sends_remove_item),
-        PROF_FUNC_TEST(sends_remove_item_nick),
-        PROF_FUNC_TEST(sends_nick_change),
     };
 
     /* ============================================================
-     * GROUP 3: Presence, Disconnect, DB History
-     * Status management, clean teardown, message persistence
+     * GROUP 3: Presence, Disconnect, DB History, Message, MUC Database
+     * Status management, message persistence, MUC storage
      * ============================================================ */
     const struct CMUnitTest group3_tests[] = {
         /* Presence - online/away/xa/dnd/chat status management */
@@ -218,11 +234,24 @@ main(int argc, char* argv[])
         PROF_FUNC_TEST(message_db_history_service_chars),
         PROF_FUNC_TEST(message_db_history_verify),
         PROF_FUNC_TEST(message_db_history_lmc),
+
+        /* Basic message send/receive */
+        PROF_FUNC_TEST(message_send),
+        PROF_FUNC_TEST(message_receive_console),
+        PROF_FUNC_TEST(message_receive_chatwin),
+
+#ifdef HAVE_SQLITE
+        /* MUC (groupchat) database — export/import of type="muc" messages */
+        PROF_FUNC_TEST(muc_export_sqlite_to_flatfile),
+        PROF_FUNC_TEST(muc_import_flatfile_to_sqlite),
+        PROF_FUNC_TEST(muc_export_timestamps_preserved),
+        PROF_FUNC_TEST(muc_export_multiple_rooms),
+#endif
     };
 
     /* ============================================================
-     * GROUP 4: Chat Session, MUC, Carbons
-     * Session routing, multi-user chat, message synchronization
+     * GROUP 4: Chat Session, MUC, Carbons, Migration Stress
+     * Session routing, multi-user chat, message sync, stress tests
      * ============================================================ */
     const struct CMUnitTest group4_tests[] = {
         /* Chat session management - bare/full JID routing */
@@ -265,6 +294,13 @@ main(int argc, char* argv[])
         PROF_FUNC_TEST(receive_carbon),
         PROF_FUNC_TEST(receive_self_carbon),
         PROF_FUNC_TEST(receive_private_carbon),
+
+#ifdef HAVE_SQLITE
+        /* Migration stress — pool accumulation, LMC chains, large bodies */
+        PROF_FUNC_TEST(export_message_pool_dated),
+        PROF_FUNC_TEST(export_lmc_pool_multiple),
+        PROF_FUNC_TEST(export_large_body_survives),
+#endif
     };
 
     /* Test group registry for easy extension */
@@ -274,10 +310,10 @@ main(int argc, char* argv[])
         const struct CMUnitTest* tests;
         size_t count;
     } groups[] = {
-        { "Group 1: Connect/Ping/Rooms/Software/LastActivity/Autoping/Disco", group1_tests, ARRAY_SIZE(group1_tests) },
-        { "Group 2: Message/Receipts/Roster/ExportImport", group2_tests, ARRAY_SIZE(group2_tests) },
-        { "Group 3: Presence/Disconnect/DBHistory", group3_tests, ARRAY_SIZE(group3_tests) },
-        { "Group 4: Session/MUC/Carbons", group4_tests, ARRAY_SIZE(group4_tests) },
+        { "Group 1: Connect/Ping/Disco/Roster", group1_tests, ARRAY_SIZE(group1_tests) },
+        { "Group 2: ExportImport/Receipts", group2_tests, ARRAY_SIZE(group2_tests) },
+        { "Group 3: Presence/Disconnect/DBHistory/Message/MUC-DB", group3_tests, ARRAY_SIZE(group3_tests) },
+        { "Group 4: Session/MUC/Carbons/MigrationStress", group4_tests, ARRAY_SIZE(group4_tests) },
     };
     const int num_groups = ARRAY_SIZE(groups);