In the current Wikimedia configuration log events emitted on testwiki go to testwiki.log only if an explicit destination is not specified for them. (Ie. if I set up, say, thumbnail.log for the 'thumbnail' channel, events in that channel don't go to testwiki.log.) Same for testwiki2.
Changing that so that such an event would go both to testwiki.log and to the specified destination might make debugging easier (as long as it does not make testwiki.log too spammy).