System.out.println("start get");
Events<Event> entrys1 = eventStore.tryGet(first, bufferSize);
System.out.println("first get size : " + entrys1.getEvents().size());
eventStore.rollback();
entrys1 = eventStore.tryGet(first, bufferSize);
System.out.println("after rollback get size : " + entrys1.getEvents().size());
Assert.assertTrue(entrys1.getEvents().size() == bufferSize / 2);