state.add(ref);
state.addReference(ref);
   public void testNonRecoverableState_remove_5() throws Throwable   {      if (state.isRecoverable())      {         // only non-recoverable state is tested now         return;      }      if (!state.acceptReliableMessages())      {         // only state that accepts reliable messages is tested now         return;      }      MessageReference ref = ms.reference(MessageFactory.createMessage("message0", true, "payload0"));      state.add(ref);      MessageReference rref = state.removeFirst();      assertEquals("message0", rref.getMessageID());      assertNull(state.removeFirst());      log.info("ok");   }