The follwoing could happen if InnoDB did some background work while
test was running:

@@ -5,6 +5,8 @@
 SELECT LOCK_MODE, LOCK_TYPE, TABLE_SCHEMA, TABLE_NAME FROM information_schema.metadata_lock_info;
 LOCK_MODE      LOCK_TYPE       TABLE_SCHEMA    TABLE_NAME
 MDL_SHARED_HIGH_PRIO   Table metadata lock     test    t1
+MDL_SHARED     Table metadata lock     mysql   innodb_table_stats
+MDL_SHARED     Table metadata lock     mysql   innodb_index_stat