Entity unit testing with PersistentEntityRegistry

I am new to lagom and I currently try to write a unit test for one of my PersistentEntity.

The constructor looks like this:
class EventEntity(persistentEntityRegistry: PersistentEntityRegistry)(implicit ex: ExecutionContext)

I am using the PersistentEntityRegistry in one of my command handlers to initialize/create another entity.

My questions:

  1. Is this the correct/idiomatic way to create new entities? So, is it ok to create one entity from within another? or should I better do this in the ServiceImpl layer after I received the reply from the command?
  2. If this is the way to go, how would I unit test this?