We have a development team built up a Data Access Layer API in Java, mimic of the EntityManager in EJB3. I am in a seperate QA team and testing it.

After communicating with the development team, we agreed that my job is to verify the object model described in UML diagram is correctly implemented(we run Strum here with no detailed spec docs).

So basically, what I need to do is to exercise the object graph through the EntityManager(to make sure I can do CRUD kind of operations). I can see development team has done quite some unit testings covered almost the while object graph. I don't really want to repeat their work.

What are the areas shall I focus on? It seems a very basic question of testing. Please give me some hints.