Spring响应式框架WebClient Builder的JUnit测试用例编写问询

要测试你这段WebClient的GET请求，我们可以用MockWebServer模拟后端服务，结合WebClient.Builder来验证请求的正确性并预设响应，完全不需要依赖真实的8080服务。

依赖准备 #

确保你的测试依赖包含这些核心库：

• spring-boot-starter-webflux：提供WebClient支持
• spring-boot-starter-test：包含JUnit 5、MockWebServer等测试工具
• okhttp3：MockWebServer的底层依赖

测试代码示例 #

先假设你的WebClient请求封装在一个业务类里（比如EmployeeService）：

@Service
public class EmployeeService {
    private final WebClient webClient;

    public EmployeeService(WebClient.Builder webClientBuilder) {
        this.webClient = webClientBuilder.baseUrl("http://localhost:8080").build();
    }

    public Mono<String> getEmployeeById(String id) {
        return webClient.get()
                .uri("/employee/{id}", id)
                .retrieve()
                .bodyToMono(String.class);
    }
}

对应的JUnit 5测试用例：

import okhttp3.mockwebserver.MockResponse;
import okhttp3.mockwebserver.MockWebServer;
import org.junit.jupiter.api.AfterAll;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import org.springframework.web.reactive.function.client.WebClient;
import reactor.test.StepVerifier;

import java.io.IOException;

class EmployeeServiceTest {
    private static MockWebServer mockWebServer;
    private EmployeeService employeeService;

    @BeforeAll
    static void startMockServer() throws IOException {
        mockWebServer = new MockWebServer();
        mockWebServer.start();
    }

    @BeforeEach
    void initService() {
        String mockBaseUrl = String.format("http://localhost:%d", mockWebServer.getPort());
        WebClient.Builder webClientBuilder = WebClient.builder().baseUrl(mockBaseUrl);
        employeeService = new EmployeeService(webClientBuilder);
    }

    @Test
    void getEmployeeById_ShouldReturnExpectedData() {
        // 预设模拟响应
        String mockEmployeeJson = "{\"id\":\"xyz\",\"name\":\"Test Employee\"}";
        mockWebServer.enqueue(new MockResponse()
                .setBody(mockEmployeeJson)
                .addHeader("Content-Type", "application/json"));

        // 调用待测试方法
        Mono<String> result = employeeService.getEmployeeById("xyz");

        // 验证响应式流的结果
        StepVerifier.create(result)
                .expectNext(mockEmployeeJson)
                .verifyComplete();

        // 验证实际发送的请求是否符合预期
        var recordedRequest = mockWebServer.takeRequest();
        assert recordedRequest.getMethod().equals("GET");
        assert recordedRequest.getPath().equals("/employee/xyz");
    }

    @AfterAll
    static void stopMockServer() throws IOException {
        mockWebServer.shutdown();
    }
}

核心要点 #

• MockWebServer：模拟后端服务，捕获发送的请求并返回预设响应，彻底隔离外部依赖
• StepVerifier：Reactor提供的工具，专门用于验证响应式流的输出是否符合预期
• 请求校验：通过takeRequest()拿到实际发送的请求，验证请求方法、路径等参数是否正确

内容的提问来源于stack exchange，提问作者Gaurav Khandelwal