public ReliableTopicConfig setTopicOverloadPolicy(TopicOverloadPolicy topicOverloadPolicy) {
        this.topicOverloadPolicy = checkNotNull(topicOverloadPolicy, "topicOverloadPolicy can't be null");
        return this;
    }
@Test(expected = NullPointerException.class)
    public void setTopicOverloadPolicy_whenNull() {
        ReliableTopicConfig config = new ReliableTopicConfig("foo");
        config.setTopicOverloadPolicy(null);
    }