And Spring does it so nicely...
I talked to Adam Bien and Jacek Laskowski about this.
Adam suggested I take a look at his x-ray application. What he does to test JPA is he instantiates EntitytManager himself for each @Test method.
EntityManagerFactory entityManagerFactory = Persistence .createEntityManagerFactory("testPu"); entityManager = entityManagerFactory.createEntityManager();
He then sets this EntityManager on the DAO/repository directly (not using a setter), on a package-level exposed field. It will not work if your DAO/repository is instantiated by CDI - you must use a package-level exposed method. Then it works (proxying).
Still, I didn't quite like this solution because it forces you to expose a field/method you wouldn't otherwise expose, and because it doesn't reflect reality where @PersistenceContext is injected.
Jacek had a different approach. One that didn't require exposing the field. You can view his test.
What he does is he uses OpenEJB to inject @PersistenceContext.
I decided I didn't like the boilerplate and I began to wonder whether Arquillian could inject @PersistenceContext for me.
Unfortunately, it turned out that Arquillian does not inject @PersistenceContext. I asked Dan Allen and Aslak Knutsen about it.
I decided it would be best if I could see whether Arquillian could do this so I forked Arquillian's source code on GitHub and I'm currently playing with it. It looks promising, so who knows, maybe it will save some hassle and boilerplate!