code: public void testOptimisticLockingThrownOnMultipleUpdates(){
    Task task=taskService.newTask();
    taskService.saveTask(task);
    String taskId=task.getId();
    Task task1=taskService.createTaskQuery().taskId(taskId).singleResult();
    Task task2=taskService.createTaskQuery().taskId(taskId).singleResult();
    task1.setDescription("first modification");
    taskService.saveTask(task1);
    task2.setDescription("second modification");
    try {
      taskService.saveTask(task2);
      fail("should get an exception here as the task was modified by someone else.");
    }
   catch (  ActivitiOptimisticLockingException expected) {
    }
    taskService.deleteTask(taskId,true);
  }
  