Add test for "MySQL databases with short system_time_zone IDs cannot sync" (#34055)

test/metabase/sync/sync_metadata/sync_timezone_test.clj

 (ns metabase.sync.sync-metadata.sync-timezone-test
   (:require
    [clj-time.core :as time]
+   [clojure.java.jdbc :as jdbc]
    [clojure.test :refer :all]
    [java-time :as t]
    [metabase.driver :as driver]
+   [metabase.driver.mysql-test :as mysql-test]
+   [metabase.driver.sql-jdbc.connection :as sql-jdbc.conn]
    [metabase.models.database :refer [Database]]
    [metabase.sync.sync-metadata.sync-timezone :as sync-tz]
    [metabase.sync.util-test :as sync.util-test]
    [metabase.test :as mt]
    [metabase.util :as u]
-   [toucan2.core :as t2]))
+   [toucan2.core :as t2]
+   [toucan2.tools.with-temp :as t2.with-temp]))
 
 (set! *warn-on-reflection* true)
 
@@ -65,3 +69,23 @@
             (is (nil? tz-after-update)))
           (testing "Check that the value was set again after sync"
             (is (time/time-zone-for-id (db-timezone db)))))))))
+
+(deftest sync-timezone-mysql-test
+  (mt/test-driver :mysql
+    (testing "sync-timezone should allow non-standard MySQL default database time zones, such as offset strings (metabase#34050)"
+      (let [details (mt/dbdef->connection-details :mysql :db {:database-name "sync_timezone_test"})
+            spec    (sql-jdbc.conn/connection-details->spec :mysql details)]
+        (mysql-test/drop-if-exists-and-create-db! "sync_timezone_test")
+        (t2.with-temp/with-temp [:model/Database database {:engine :mysql, :details (assoc details :dbname "sync_timezone_test")}]
+          (let [global-time-zone (-> (jdbc/query spec ["SELECT @@GLOBAL.time_zone;"])
+                                     first
+                                     (get (keyword "@@global.time_zone")))]
+            (try
+              (jdbc/execute! spec ["SET GLOBAL time_zone = '+8:00';"])
+              (let [{:keys [step-info]} (sync.util-test/sync-database! "sync-timezone" database)]
+                (is (= {:timezone-id "+08:00"}
+                       (sync.util-test/only-step-keys step-info)))
+                (is (= "+08:00"
+                       (t2/select-one-fn :timezone :model/Database (:id database)))))
+              (finally
+                (jdbc/execute! spec [(str "SET GLOBAL time_zone = '" global-time-zone "';")])))))))))