@Override
    public void shutdown() throws InterruptedException {
        Optional<MockTask> currentTask;
        do {
            currentTask = poll(t -> true);
            currentTask.ifPresent(t -> t.task.run());
        } while (currentTask.isPresent());
    }
Not used, so not fully implemented
server-common/src/test/java/org/apache/kafka/server/util/MockScheduler.java