Testing Active Objects : java.lang.IllegalStateException: There are two concurrently open transactions!

Hi Everyone,
I am trying to test active object accessor methods. I am getting an error

“java.lang.IllegalStateException: There are two concurrently open transactions!”

I am pretty sure that all the written tests are concurrent and I think the test runner class while trying to reset the database is doing something which is causing this error to occur. Because I am getting this error after the test case has run.

This is my DatabaseUpdater class ->

@Test
    public void createEntry()throws Exception{
        final AModel entry = aAccessor.createEntry(model);
        System.out.println(entry.getApp());
        assertNull(entry);
    }

    public static class AAccessorImplTestDatabaseUpdater implements DatabaseUpdater {

        @Override
        public void update(EntityManager em) throws Exception {
            em.migrate(A.class);
            ao = new TestActiveObjects(em);
            ao.executeInTransaction(() -> {
                final A a = ao.create(A.class);
                a.setApp("GSP");
                a.setComp("");
                a.setIns("");
                a.setPro("");
                a.save();
                return a;
            });
            ao.flushAll();
        }
    }

and this the method I am testing

@Nullable
    public AModel createEntry(AModel model) throws NullArgumentException {
        if (!validateEntry(model)) {
            return null;
        }
        final AModel aModel = ao.executeInTransaction(() -> {
            final A m = ao.create(A.class);
            m.setApp(model.getApp());
            m.setIns(model.getIns());
            m.setPro(model.getPro());
            m.setComp(model.getComp());
            m.save();
            m.setID(m.getID());
            return model;
        });
        ao.flushAll(); //added to because of error
        return aModel;
    }