我´我现在正在做噩梦测试我的spring webclient代码。给出以下简单方法

private String request(String uri, String body) {
    return webClient
            .method(HttpMethod.POST)
            .uri(uri)
            .body(Mono.just(body), String.class)
            .retrieve()
            .bodyToMono(String.class)
            .block();
}

以及以下单元测试：

@Before
public void setUp() throws IOException {
    baseUrl = "http://localhost:%s";
    mockWebServer = new MockWebServer();
    mockWebServer.start();
    int mockWebServerPort = mockWebServer.getPort();
    baseUrl = String.format(baseUrl, mockWebServerPort);
    webClient = WebClient.create();
}

 @After
public void shutdown() throws IOException {
    mockWebServer.shutdown();
}

    @Test
public void testPost() throws InterruptedException {
    String body = "Hello";
    givenMockResponse(response -> {
        response.setResponseCode(200);
        response.setBody(body);
    });
    request(baseUrl, body);
    RecordedRequest recordedRequest = mockWebServer.takeRequest();
    checkRequest(recordedRequest);
}

当我通过intellij运行测试时它通过了，但是当我´m使用maven时会引发以下异常：

reactor.core.Exceptions$ReactiveException: java.util.concurrent.TimeoutException: Did not observe any item or terminal signal within 0ms in 'flatMap' (and no fallback has been configured)

当我启动spring启动应用程序并手动测试它时，request方法也可以正常运行。我的项目使用springboot2.3.1，mavensurefire-plugin:3.0.0-m3，jdk 11和用于使用okhttp3 mockwebserver 4.0.1测试junit4。你知道这个问题是由什么引起的吗？