Config fragment:

$_CONFIG['Databases'] = array(
  array(
	'DBHost' => 'host_of_1st_slave',
	'DBUser' => 'user_of_1st_slave',
	'DBUserPassword' => 'password_of_1st_slave',
	'DBLoad' => 1, // means 100% of slave load would go to this slave
  ),
);

1. add the Databases key to /system/config.php that would look like above (maybe same database server can be used as slave too for testing purposes)
2. configure a separate database server with slave database and replication from master
3. trigger some errror to create record in System Log section
4. place a following code in any event, that you can trigger: $this->Application->deleteLog(unique_id) (replace unique_id with value from LogUniqueId column of any record in System Log section)
5. confirm, that chosen record was removed from database