I would like your ideas about unit testing in hibernate. I'm not thinking about dao mockups or using a in-memory database which I already use anyway.

The recurring design problem that I have when unit testing my domain class is that some class have mandatory dependencies on other classes (e.g. "many-to-one" with "not-null" constraint relationships), so to test persistence on a given object, all its dependencies have to be first persisted correctly which indirectly means that all other dependencies must be already unit-tested (given I'm using a test driven development approach). I always end-up creating lots of hibernate mapping files before being able to unit test the persistence of a single class, so my unit tests look more like integration tests. When a particular domain object unit test fails because of an invalid mapping attribute or any other persistence error, all other unit tests that depends on that domain object basically fail too. So, this kind of breaks the isolation of my unit tests.

What do you do to prevent this situation?

1) You don't unit test the persistence of a domain class, you just test the persistence at the DAOs level?
2) You test top-down, so parent objects are tested before child objects
3) You don't map dependencies that are not mapped yet (you come back to complete your unit test when they are)

I was thinking of an approach where dependencies would be mapped differently in my unit test. Let say that I have a "CustomerBill" class that refers to a "Customer" class. I want to unit test the persistence of the "CustomerBill" without depending on the "real" mapping of the "Customer" class. So my "CustomerBill" unit test could load a configuration where the "Customer" would be simply mapped as a table with an id, with no other fields. This way, the "CustomerBill" could be persisted along with its "many-to-one" relationship to the "Customer".

For sure, I don't want to create different "hbm.xml" for all my test classes, I was rather thinking of a programmatic way to generate them. Let's say something similar to the "Configuration.addClass(Class classToMap)".



That's the beginning of an idea...