MockWebServer is making actual calls to my service instead of mocking them

I am currently developing a microservices app using Spring Boot. I am attempting to write a test for my user-service WebClient using MockWebServer. However, it appears that MockWebServer is sending a real request to the service instead of mocking it. This issue persists even when the service is running, likely due to my usage of Eureka discovery for service registration.

public class UserClientTest {
    private MockWebServer mockWebServer;
    private UserClient userClient;
    @Autowired
    WebClient.Builder webClientBuilder;

    @BeforeEach
    public void setup() throws IOException {
        mockWebServer = new MockWebServer();
        mockWebServer.start();

        webClientBuilder = WebClient.builder()
                .baseUrl(mockWebServer.url("/users").toString());
        userClient = new UserClient(webClientBuilder);
    }

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

    @Test
    @DisplayName("Should create a new user")
    public void shouldCreateANewUser() {
        UserResponse mockResponse = new UserResponse(1L, "john_doe", "john@example.com");
        mockWebServer.enqueue(
                new MockResponse().setResponseCode(201)
                .setHeader(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE)
                .setBody(new Gson().toJson(mockResponse))
        );

        // Perform the actual method call
        UserRequest userRequest = new UserRequest("john_doe", "password", "john@example.com");
        Mono<UserResponse> createUserMono = userClient.createUser(userRequest);
        StepVerifier.create(createUserMono)
                .expectNext(mockResponse)
                .verifyComplete();
    }

}

@Component
public class UserClient {
    private static final String BASE_URL = "http://user-service";
    private final WebClient webClient;

    public UserClient(@Autowired WebClient.Builder webClient) {
        this.webClient = webClient.baseUrl(BASE_URL).build();
    }

    public Mono<UserResponse> createUser(UserRequest userRequest) {
        return webClient.post()
                .uri("/users")
                .bodyValue(userRequest)
                .retrieve()
                .bodyToMono(UserResponse.class);
    }
}

@Configuration
public class WebClientConfig {

    @Bean
    @LoadBalanced
    public WebClient.Builder webClientBuilder() {
        return WebClient.builder();
    }
}

I think it is because the following UserClient 's constructor always fix the WebClient 's base URL to http://user-service which override the setting you configure in the test :

@Component
public class UserClient {
    public static final String BASE_URL = "http://user-service";
    private final WebClient webClient;

    public UserClient(@Autowired WebClient.Builder webClient) {
        this.webClient = webClient.baseUrl(BASE_URL).build();
    }
}

To be more flexible , it should respect the setting of the input WebClient.Builder :

    public UserClient(@Autowired WebClient.Builder webClient) {
        this.webClient = webClient.build();
    }

The client can then define the base URL by themself such as :

@Configuration
public class WebClientConfig {

    @Bean
    @LoadBalanced
    public WebClient.Builder webClientBuilder() {
        return WebClient.builder().baseUrl(UserClient.BASE_URL);
    }
}