如何模拟Spring WebFlux WebClient？

Question

我们编写了一个小型Spring Boot REST应用程序，它在另一个RESTendpoint上执行REST请求。

@RequestMapping("/api/v1")
@SpringBootApplication
@RestController
@Slf4j
public class Application
{
    @Autowired
    private WebClient webClient;

    @RequestMapping(value = "/zyx", method = POST)
    @ResponseBody
    XyzApiResponse zyx(@RequestBody XyzApiRequest request, @RequestHeader HttpHeaders headers)
    {
        webClient.post()
            .uri("/api/v1/someapi")
            .accept(MediaType.APPLICATION_JSON)
            .contentType(MediaType.APPLICATION_JSON)
            .body(BodyInserters.fromObject(request.getData()))
            .exchange()
            .subscribeOn(Schedulers.elastic())
            .flatMap(response ->
                    response.bodyToMono(XyzServiceResponse.class).map(r ->
                    {
                        if (r != null)
                        {
                            r.setStatus(response.statusCode().value());
                        }

                        if (!response.statusCode().is2xxSuccessful())
                        {
                            throw new ProcessResponseException(
                                    "Bad status response code " + response.statusCode() + "!");
                        }

                        return r;
                    }))
            .subscribe(body ->
            {
                // Do various things
            }, throwable ->
            {
                // This section handles request errors
            });

        return XyzApiResponse.OK;
    }
}

我们是Spring新手，在为这个小代码段编写单元测试时遇到了困难。

是否有一种优雅的（反应式）方式来模拟webClient本身或启动webClient可以用作endpoint的模拟服务器？

Answer 1

OkHttp团队可以使用MockWebServer。基本上，Spring团队也将其用于测试（至少他们在这里是这样说的）。以下是一个参考源的示例：

根据Tim的博客文章，让我们考虑一下我们有以下服务：

class ApiCaller {
    
   private WebClient webClient;
    
   ApiCaller(WebClient webClient) {
      this.webClient = webClient;
   }
    
   Mono<SimpleResponseDto> callApi() {
       return webClient.put()
                       .uri("/api/resource")
                       .contentType(MediaType.APPLICATION_JSON)
                       .header("Authorization", "customAuth")
                       .syncBody(new SimpleRequestDto())
                       .retrieve()
                       .bodyToMono(SimpleResponseDto.class);
    }
}

然后可以按照以下方式设计测试（与origin相比，我改变了异步链在Reactor中使用StepVerifier进行测试的方式）：

class ApiCallerTest {
  
  private final MockWebServer mockWebServer = new MockWebServer();
  private final ApiCaller apiCaller = new ApiCaller(WebClient.create(mockWebServer.url("/").toString()));
  
  @AfterEach
  void tearDown() throws IOException {
     mockWebServer.shutdown();
  }
  
  @Test
  void call() throws InterruptedException {
       mockWebServer.enqueue(new MockResponse().setResponseCode(200)
                                               .setHeader(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE)
                                               .setBody("{\"y\": \"value for y\", \"z\": 789}")
      );
      
      //Asserting response
      StepVerifier.create(apiCaller.callApi())
                  .assertNext(res -> {
                        assertNotNull(res);
                        assertEquals("value for y", res.getY());
                        assertEquals("789", res.getZ());
                  })
                  .verifyComplete();
 
     //Asserting request
     RecordedRequest recordedRequest = mockWebServer.takeRequest();
     //use method provided by MockWebServer to assert the request header
     recordedRequest.getHeader("Authorization").equals("customAuth");
     DocumentContext context = >JsonPath.parse(recordedRequest.getBody().inputStream());
     //use JsonPath library to assert the request body
     assertThat(context, isJson(allOf(
            withJsonPath("$.a", is("value1")),
            withJsonPath("$.b", is(123))
     )));
  }
}

Answer 2

使用以下方法，可以使用Mockito模拟WebClient进行以下调用：

webClient
.get()
.uri(url)
.header(headerName, headerValue)
.retrieve()
.bodyToMono(String.class);

或

webClient
.get()
.uri(url)
.headers(hs -> hs.addAll(headers));
.retrieve()
.bodyToMono(String.class);

模拟方法：

private static WebClient getWebClientMock(final String resp) {
    final var mock = Mockito.mock(WebClient.class);
    final var uriSpecMock = Mockito.mock(WebClient.RequestHeadersUriSpec.class);
    final var headersSpecMock = Mockito.mock(WebClient.RequestHeadersSpec.class);
    final var responseSpecMock = Mockito.mock(WebClient.ResponseSpec.class);

    when(mock.get()).thenReturn(uriSpecMock);
    when(uriSpecMock.uri(ArgumentMatchers.<String>notNull())).thenReturn(headersSpecMock);
    when(headersSpecMock.header(notNull(), notNull())).thenReturn(headersSpecMock);
    when(headersSpecMock.headers(notNull())).thenReturn(headersSpecMock);
    when(headersSpecMock.retrieve()).thenReturn(responseSpecMock);
    when(responseSpecMock.bodyToMono(ArgumentMatchers.<Class<String>>notNull()))
            .thenReturn(Mono.just(resp));

    return mock;
}

Answer 3

我们通过提供一个自定义的ExchangeFunction来实现这一点，该函数只需将我们想要的响应返回给WebClient Builder：

webClient = WebClient.builder()
            .exchangeFunction(clientRequest -> 
                    Mono.just(ClientResponse.create(HttpStatus.OK)
                    .header("content-type", "application/json")
                    .body("{ \"key\" : \"value\"}")
                    .build())
            ).build();

myHttpService = new MyHttpService(webClient);

Map<String, String> result = myHttpService.callService().block();

// Do assertions here
    

如果我们想使用Mokcito来验证是否进行了调用或在类中的多个单元测试中重用WebClient，我们还可以模拟交换函数：

@Mock
private ExchangeFunction exchangeFunction;

@BeforeEach
void init() {
    WebClient webClient = WebClient.builder()
            .exchangeFunction(exchangeFunction)
            .build();

    myHttpService = new MyHttpService(webClient);
}

@Test
void callService() {
    when(exchangeFunction.exchange(any(ClientRequest.class)))
   .thenReturn(buildMockResponse());
    Map<String, String> result = myHttpService.callService().block();

    verify(exchangeFunction).exchange(any());

    // Do assertions here
}
    

注意：如果在调用时得到与发布者相关的空指针异常，则IDE可能已导入Mono。而不是Mockito。当 。

来源：

• WebClient javadoc