### Question:
TimerSchedulerServiceImpl extends BaseOpenmrsService implements SchedulerService { @Override public Task scheduleTask(TaskDefinition taskDefinition) throws SchedulerException { Task clientTask = null; if (taskDefinition != null) { TimerSchedulerTask schedulerTask = scheduledTasks.get(taskDefinition.getId()); if (schedulerTask != null) { log.info("Shutting down the existing instance of this task to avoid conflicts!!"); schedulerTask.shutdown(); } try { clientTask = TaskFactory.getInstance().createInstance(taskDefinition); if (clientTask != null) { schedulerTask = new TimerSchedulerTask(clientTask); taskDefinition.setTaskInstance(clientTask); long repeatInterval = 0; if (taskDefinition.getRepeatInterval() != null) { repeatInterval = taskDefinition.getRepeatInterval() * SchedulerConstants.SCHEDULER_MILLIS_PER_SECOND; } if (taskDefinition.getStartTime() != null) { Date nextTime = SchedulerUtil.getNextExecution(taskDefinition); log.info("Starting task ... the task will execute for the first time at " + nextTime); if (repeatInterval > 0) { getTimer(taskDefinition).scheduleAtFixedRate(schedulerTask, nextTime, repeatInterval); } else { getTimer(taskDefinition).schedule(schedulerTask, nextTime); } } else if (repeatInterval > 0) { log.info("Delaying start time by " + SchedulerConstants.SCHEDULER_DEFAULT_DELAY + " seconds"); getTimer(taskDefinition).scheduleAtFixedRate(schedulerTask, SchedulerConstants.SCHEDULER_DEFAULT_DELAY, repeatInterval); } else { log.info("Starting one-shot task"); getTimer(taskDefinition).schedule(schedulerTask, new Date()); } log.debug("Registering timer for task " + taskDefinition.getId()); scheduledTasks.put(taskDefinition.getId(), schedulerTask); taskDefinition.setStarted(true); saveTaskDefinition(taskDefinition); } } catch (Exception e) { log.error("Failed to schedule task " + taskDefinition.getName(), e); throw new SchedulerException("Failed to schedule task", e); } } return clientTask; }  SchedulerDAO getSchedulerDAO(); void setSchedulerDAO(SchedulerDAO dao); @Override void onStartup(); static void setScheduledTasks(Map<Integer, TimerSchedulerTask> scheduledTasks); @Override void onShutdown(); void shutdownAllTasks(); @Override Task scheduleTask(TaskDefinition taskDefinition); @Override void shutdownTask(TaskDefinition taskDefinition); @Override void rescheduleAllTasks(); @Override Task rescheduleTask(TaskDefinition taskDefinition); void registerTask(TaskDefinition definition); @Override Collection<TaskDefinition> getScheduledTasks(); @Override @Transactional(readOnly = true) Collection<TaskDefinition> getRegisteredTasks(); @Override @Transactional(readOnly = true) TaskDefinition getTask(Integer id); @Override @Transactional(readOnly = true) TaskDefinition getTaskByName(String name); @Override void saveTaskDefinition(TaskDefinition task); @Override void deleteTask(Integer id); @Override SortedMap<String, String> getSystemVariables(); @Override OpenmrsMemento saveToMemento(); @Override @SuppressWarnings("unchecked") void restoreFromMemento(OpenmrsMemento memento); @Override String getStatus(Integer id); @Override void scheduleIfNotRunning(TaskDefinition taskDef);  }### Answer:
@Test public void scheduleTask_shouldHandleZeroRepeatInterval() throws SchedulerException { Calendar startTime = Calendar.getInstance(); Long repeatInterval = 0L; String taskName = "TestTask"; String className = "org.openmrs.scheduler.tasks.TestTask"; Boolean startOnStartup = false; TaskDefinition taskDefinition = new TaskDefinition(); taskDefinition.setName(taskName); taskDefinition.setTaskClass(className); taskDefinition.setStartTime(startTime.getTime()); taskDefinition.setRepeatInterval(repeatInterval); taskDefinition.setStartOnStartup(startOnStartup); Task clientTask = null; clientTask = Context.getSchedulerService().scheduleTask(taskDefinition); Context.flushSession(); assertNotNull( "The clientTask variable is null, so either the TimerSchedulerServiceImpl.scheduleTask method hasn't finished or didn't get run", clientTask); }