@Test
void topicNum() {

    domainBuilder.topicMessage(t -> t.topicNum(0)).block();
    domainBuilder.topicMessage(t -> t.topicNum(1)).block();
    domainBuilder.topicMessage(t -> t.topicNum(2)).block();
    TopicMessageFilter filter = TopicMessageFilter.builder()
            .startTime(Instant.EPOCH)
            .topicNum(1)
            .build();
    pollingTopicMessageRetriever.retrieve(filter)
            .map(TopicMessage::getSequenceNumber)
            .as(StepVerifier::create)
            .expectNext(2L)
            .thenCancel()
            .verify(Duration.ofMillis(500));
}