code: public void testQueryByInvolvedGroup(){
    try {
      Task adhocTask=taskService.newTask();
      adhocTask.setAssignee(KERMIT);
      adhocTask.setOwner(FOZZIE);
      taskService.saveTask(adhocTask);
      taskService.addGroupIdentityLink(adhocTask.getId(),"group1",IdentityLinkType.PARTICIPANT);
      List<String> groups=new ArrayList<String>();
      groups.add("group1");
      assertEquals(3,taskService.getIdentityLinksForTask(adhocTask.getId()).size());
      assertEquals(1,taskService.createTaskQuery().taskId(adhocTask.getId()).taskInvolvedGroupsIn(groups).count());
    }
    finally {
      List<Task> allTasks=taskService.createTaskQuery().list();
      for (    Task task : allTasks) {
        if (task.getExecutionId() == null) {
          taskService.deleteTask(task.getId());
          if (processEngineConfiguration.getHistoryLevel().isAtLeast(HistoryLevel.AUDIT)) {
            historyService.deleteHistoricTaskInstance(task.getId());
          }
        }
      }
    }
  }
  