我开始将Spring WebFlux集成到我们的项目中，最近遇到了一个关于Flux.flatMap()的问题，下面的代码总结了这个问题：

@Component
@RequiredArgsConstructor
public class Client {

    private final ParameterizedTypeReference<List<ResponseDto>> TYPE = new ParameterizedTypeReference<>() {
    };

    private final WebClient webClient;

    public Mono<List<ResponseDto>> queryData(List<RequestDto> request) {
        return webClient.post()
                .uri("/api/query-data")
                .bodyValue(request)
                .retrieve()
                .bodyToMono(TYPE);
    }
}

@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.DEFINED_PORT)
class DemoApplicationTest {
    static final int COUNT = 1000_000;

    @Autowired
    private Client client;

    @Test
    void requestsAreSent() {
        List<RequestDto> requests = getRequests();
        List<List<RequestDto>> partition = Lists.partition(requests, 1000);
        Flux.fromIterable(partition)
                .flatMap(client::queryData)
                .collectList()
                .block();
    }

    @Test
    void requestsAreNotSent() {
        List<RequestDto> requests = getRequests();
        List<List<RequestDto>> partition = Lists.partition(requests, 1000);
        Flux.fromIterable(partition)
                .map(client::queryData)
                .collectList()
                .block();
    }

    private static List<RequestDto> getRequests() {
        return IntStream.range(0, COUNT)
                .boxed()
                .map(operand -> RequestDto.builder().build())
                .collect(Collectors.toList());
    }
}

如果我使用Flux.flatMap()，我会看到我的测试向webserver发送请求，但是如果我使用Flux.map()，则不会发送请求。
有人能解释这种行为吗？是固有的还是我配置错了？