Load tests with transactions but using JUnit

Question

I would like to to load tests in JUnit. The scenario is the following: I want to test the EJB3 with their transactions, with the EntityManager, and a memory database. For the load test I'm using ContiPerf 2. I googled it and I saw different approaches. In some of then they were using a embedded EJBContainer, in another they were just initializing the EntityManager and they were starting the transaction from the EntityTransaction.

For a simple unit test, with the EntityManager and the EntityTransaction is enough, but when I want to do a load test I find several problems, but the biggest one it's conceptual.

My first approach was this:

@Test
@PerfTest(invocations = 1000, threads = 5)
@Required(max = 1000, average = 250)
public void testTransaction() {
    et.begin();
    MyEntity myEntity = new MyEntity();
    service.performAction(myEntity);
    thenMyEntityIsOk(myEntity);
    et.rollback();
}

But in this test I had problems doing the load test because of the rollback (if instead of a rollback I use commit the problem is the same).

After this I thought that maybe the problem could be the transactions, then I start using the embedded EJBContainer, but I had a lot of problems with the dependencies and with the execution.

Do you have any suggestion about how to do a load test in JUnit?