self.retry doesn't retry the task on unittests

[skinderis]

I have a celery task which base class is QueueOnce, the task is locked with order_id argument:

@app.task(
    bind=True,
    soft_time_limit=settings.SOFT_TIME_LIMIT,
    base=QueueOnce,
    once={'keys': ['order_id'],
          'graceful': False}
)
def some_celery_task_invoke(self, order_id, **kwargs):
    task = SomeTask()
    retry, res = task.run()
    ...
    if retry:
        try:
            retry_parameters = {
                'kwargs': res,
                'countdown': delay_seconds,
                'max_retries': max_retries,
                'soft_time_limit': time_limit,
            }
            self.retry(**retry_parameters)
        except exceptions.MaxRetriesExceededError:
            logger.info('Some logging')

This task works well and retries are working as well when I am testing it on dev environment. But, when I run a unittest to check if retries are working, task call self.retry(**retry_parameters) - it doesn't initiate some_celery_task_invoke. What could be the reason?