Spring WebClient的单元测试

WebClient引用其Java文档是Spring Framework的

非阻塞，反应式客户端执行HTTP请求，通过底层HTTP客户端库（如Reactor Netty）公开流利的，反应式API 。

在我当前的项目中，我广泛使用WebClient进行服务到服务的调用，并发现它是一个了不起的API，并且我喜欢使用Fluent接口。

考虑一个返回“城市”列表的远程服务。使用WebClient的代码如下所示：

 ...  import org.springframework.http.MediaType  import org.springframework.web.reactive.function.client.WebClient  import org.springframework.web.reactive.function.client.bodyToFlux  import org.springframework.web.util.UriComponentsBuilder  import reactor.core.publisher.Flux  import java.net.URI  CitiesClient( class CitiesClient( private val webClientBuilder: WebClient.Builder, private val citiesBaseUrl: String  ) { fun getCities(): Flux<City> { val buildUri: URI = UriComponentsBuilder .fromUriString(citiesBaseUrl) .path( "/cities" ) .build() .encode() .toUri() val webClient: WebClient = this .webClientBuilder.build() return webClient.get() .uri(buildUri) .accept(MediaType.APPLICATION_JSON) .exchange() .flatMapMany { clientResponse -> clientResponse.bodyToFlux<City>() } }  }

但是，很难测试使用WebClient的客户端。在本文中，我将介绍使用WebClient和干净的解决方案测试客户端的挑战。

模拟WebClient的挑战

要对“ CitiesClient”类进行有效的单元测试，将需要模拟WebClient以及流利的接口链中的每个方法调用，包括：

 val mockWebClientBuilder: WebClient.Builder = mock()  val mockWebClient: WebClient = mock()  whenever(mockWebClientBuilder.build()).thenReturn(mockWebClient)  val mockRequestSpec: WebClient.RequestBodyUriSpec = mock()  whenever(mockWebClient.get()).thenReturn(mockRequestSpec)  val mockRequestBodySpec: WebClient.RequestBodySpec = mock()  whenever(mockRequestSpec.uri(any<URI>())).thenReturn(mockRequestBodySpec)  whenever(mockRequestBodySpec.accept(any())).thenReturn(mockRequestBodySpec)  val citiesJson: String = this .javaClass.getResource( "/sample-cities.json" ).readText()  val clientResponse: ClientResponse = ClientResponse .create(HttpStatus.OK) .header( "Content-Type" , "application/json" ) .body(citiesJson).build()  whenever(mockRequestBodySpec.exchange()).thenReturn(Mono.just(clientResponse))  val citiesClient = CitiesClient(mockWebClientBuilder, " http://somebaseurl " )  val cities: Flux<City> = citiesClient.getCities()

这使得测试非常不稳定，因为调用顺序的任何更改都将导致需要记录新的模拟。

使用真实端点进行测试

一种行之有效的方法是启动行为类似于客户端目标的真实服务器。 okhttp库和WireMock中的两个模拟服务器运行得很好，它们是模拟服务器。 Wiremock的示例如下所示：

 import com.github.tomakehurst.wiremock.WireMockServer  import com.github.tomakehurst.wiremock.client.WireMock  import com.github.tomakehurst.wiremock.core.WireMockConfiguration  import org.bk.samples.model.City  import org.junit.jupiter.api.AfterAll  import org.junit.jupiter.api.BeforeAll  import org.junit.jupiter.api.Test  import org.springframework.http.HttpStatus  import org.springframework.web.reactive.function.client.WebClient  import reactor.core.publisher.Flux  import reactor.test.StepVerifier  WiremockWebClientTest { class WiremockWebClientTest { @Test fun testARemoteCall() { val citiesJson = this .javaClass.getResource( "/sample-cities.json" ).readText() WIREMOCK_SERVER.stubFor(WireMock.get(WireMock.urlMatching( "/cities" )) .withHeader( "Accept" , WireMock.equalTo( "application/json" )) .willReturn(WireMock.aResponse() .withStatus(HttpStatus.OK.value()) .withHeader( "Content-Type" , "application/json" ) .withBody(citiesJson))) val citiesClient = CitiesClient(WebClient.builder(), " http://localhost: ${WIREMOCK_SERVER.port()}" ) val cities: Flux<City> = citiesClient.getCities()         StepVerifier .create(cities) .expectNext(City(1L, "Portland" , "USA" , 1_600_000L)) .expectNext(City(2L, "Seattle" , "USA" , 3_200_000L)) .expectNext(City(3L, "SFO" , "USA" , 6_400_000L)) .expectComplete() .verify() } companion object { private val WIREMOCK_SERVER = WireMockServer(WireMockConfiguration.wireMockConfig().dynamicPort()) @BeforeAll @JvmStatic fun beforeAll() { WIREMOCK_SERVER.start() } @AfterAll @JvmStatic fun afterAll() { WIREMOCK_SERVER.stop() } }  }

在这里，服务器是通过随机端口启动的，然后注入行为，然后针对该服务器测试客户端并进行验证。这种方法有效，并且在模拟此行为时不会与WebClient的内部混淆，但是从技术上讲，这是一个集成测试，并且比纯单元测试执行起来要慢。

通过使远程呼叫短路来进行单元测试

我最近使用的一种方法是使用ExchangeFunction短路远程调用。 ExchangeFunction代表进行远程调用的实际机制，可以用一种以测试期望的方式响应的方式代替ExchangeFunction：

 import org.junit.jupiter.api.Test  import org.springframework.http.HttpStatus  import org.springframework.web.reactive.function.client.ClientResponse  import org.springframework.web.reactive.function.client.ExchangeFunction  import org.springframework.web.reactive.function.client.WebClient  import reactor.core.publisher.Flux  import reactor.core.publisher.Mono  import reactor.test.StepVerifier  CitiesWebClientTest { class CitiesWebClientTest { @Test fun testCleanResponse() { val citiesJson: String = this .javaClass.getResource( "/sample-cities.json" ).readText() val clientResponse: ClientResponse = ClientResponse .create(HttpStatus.OK) .header( "Content-Type" , "application/json" ) .body(citiesJson).build() val shortCircuitingExchangeFunction = ExchangeFunction { Mono.just(clientResponse) } val webClientBuilder: WebClient.Builder = WebClient.builder().exchangeFunction(shortCircuitingExchangeFunction) val citiesClient = CitiesClient(webClientBuilder, " http://somebaseurl " ) val cities: Flux<City> = citiesClient.getCities() StepVerifier .create(cities) .expectNext(City(1L, "Portland" , "USA" , 1_600_000L)) .expectNext(City(2L, "Seattle" , "USA" , 3_200_000L)) .expectNext(City(3L, "SFO" , "USA" , 6_400_000L)) .expectComplete() .verify() }  }

WebClient注入了ExchangeFunction，该函数仅返回具有远程服务器预期行为的响应。这使整个远程呼叫短路，并允许对客户端进行全面测试。这种方法取决于对WebClient内部的一点了解。虽然这是一个不错的妥协，但是它的运行速度比使用WireMock进行的测试要快得多。

但是这种方法不是原始的，我已经基于用于测试WebClient本身的一些测试来建立此测试，例如，此处的