问题
Should Rich Domain Models have interfaces to assist with isolation during unit testing (e.g. when testing a service that uses the model)?
Or should the Rich Domain Model behaviour be involved in any related unit tests?
Edit:
By Rich Domain Model I'm specifically referring to domain entities that contain logic (i.e. non-anaemic).
回答1:
Usually, the Domain Model is the part that you should keep isolated from everything else. The Domain Model may use interfaces so that it's isolated from external systems, etc.
However, in the most common scenarios, the Domain Model is what you're trying to protect from the deteriorating influences of external systems, UI logic, etc. - not the other way around.
Thus, there's little reason to put interfaces on the Domain Model.
回答2:
You should definitely involve domain model behaviour in your unit tests. There's absolutely no point in mocking this part. You should really only be mocking external systems.
回答3:
Should Rich Domain Models have interfaces
I'd say no, because
Domain behavior happens inside a well-delimited bubble. A given command triggers changes in a single aggregate. Conceptually, you don't have to isolate it since it basically just talks to itself. It might also issue messages (events) to the outside world, but testing that doesn't require the domain entities themselves to be mockable.
Concretely, domain entity (or value object) behavior is fluid -- it happens all in memory and is not supposed to directly call lower level, I/O bound operations. There will be no performance impact to not mocking stuff in your tests as long as the system under test is a small prepared cluster of objects (the Aggregate and maybe the thing calling it).
Domain model is a realm of concrete concepts. Ubiquitous language terms reflected in your entity or value object class/method names are usually prosaic and unequivocal. There's not much need for abstraction and polymorphism there -- which is what interfaces or abstract classes are for. The domain is less about generic contracts or interfaces providing services, and more about real world tasks that take place in the problem domain.
来源：https://stackoverflow.com/questions/29253606/interfaces-for-rich-domain-models