Logger logger = LoggerFactory.getLogger("test");
LogbackListAppender appender = new LogbackListAppender();
appender.addToLogger("test");
// time not enough to shutdown,write error log.
appender.clearLogs();
ExecutorService pool = Executors.newSingleThreadExecutor();
Runnable task = new Task(logger, 1000, 0);
pool.execute(task);
Threads.normalShutdown(pool, 500, TimeUnit.MILLISECONDS);
assertThat(pool.isTerminated()).isTrue();