Clarification of multi-db capabilities

[sriedel]

The README states

#db defaults to the default Mongoid database, but can be specified manually in a few ways:

querying DatabaseCleaner[:mongoid].db returns :default, however I do not have a database called default, yet DatabaseCleaner works as expected. I do have a Mongoid client configured via mongoid.yml called default, though.

When attempting to tell DatabaseCleaner to clean database that is referenced via a differently named client, I need to supply the other clients name to DatabaseCleaner[:mongoid].db instead of the actual databases name for things to work as expected. Specifying DatabaseCleaner[:mongoid, db: :actual_database_name].start and ...clean does not work.

So it seems that the #db method is a misnomer and instead accesses Mongoid.clients[DatabaseCleaner[:mongoid].db] to resolve the actual clients/databases to clean (deduced from observed behavior, I didn't check in the code).

Could you please clarify what the actual configuration should be? Also, is it possible to have DatabaseCleaner handle multiple databases/clients/sessions at once, and if so, how would that be configured?