> The test DB was created using the management mbean. How can I
> specify the database encoding in that?

No chance. For some reasons Firebird ignores it even it is specified, the
only possibility is to update the system table RDB$DATABASE (please check in
Firebird-Support, if new versions of Firebird are ok with this):

UPDATE
rdb$database
SET
rdb$character_set_name = 'UNICODE_FSS'


Or you define the encoding for each created column...

Roman