code: public void testBasicJobExecutorOperation() throws Exception {
    CommandExecutor commandExecutor=processEngineConfiguration.getCommandExecutor();
    commandExecutor.execute(new Command<Void>(){
      public Void execute(    CommandContext commandContext){
        JobManager jobManager=commandContext.getJobManager();
        jobManager.execute(createTweetMessage("message-one"));
        jobManager.execute(createTweetMessage("message-two"));
        jobManager.execute(createTweetMessage("message-three"));
        jobManager.execute(createTweetMessage("message-four"));
        TimerJobEntityManager timerJobManager=commandContext.getTimerJobEntityManager();
        timerJobManager.insert(createTweetTimer("timer-one",new Date()));
        timerJobManager.insert(createTweetTimer("timer-one",new Date()));
        timerJobManager.insert(createTweetTimer("timer-two",new Date()));
        return null;
      }
    }
  );
    GregorianCalendar currentCal=new GregorianCalendar();
    currentCal.add(Calendar.MINUTE,1);
    processEngineConfiguration.getClock().setCurrentTime(currentCal.getTime());
    waitForJobExecutorToProcessAllJobs(8000L,200L);
    Set<String> messages=new HashSet<String>(tweetHandler.getMessages());
    Set<String> expectedMessages=new HashSet<String>();
    expectedMessages.add("message-one");
    expectedMessages.add("message-two");
    expectedMessages.add("message-three");
    expectedMessages.add("message-four");
    expectedMessages.add("timer-one");
    expectedMessages.add("timer-two");
    assertEquals(new TreeSet<String>(expectedMessages),new TreeSet<String>(messages));
  }
  