WebTestClient
Version 5.2.6.RELEASE
WebTestClient is a thin shell around WebClient, using it to perform requests and
exposing a dedicated, fluent API for verifying responses. WebTestClient binds to
a WebFlux application by using a mock request and response, or it can test any
web server over an HTTP connection.
Kotlin users: See this section related to use of the WebTestClient.
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Chapter 1. Setup
To create a WebTestClient you must choose one of several server setup options. Effectively you’re
either configuring the WebFlux application to bind to or using a URL to connect to a running
server.
1.1. Bind to Controller
The following example shows how to create a server setup to test one @Controller at a time:
Java
client = WebTestClient.bindToController(new TestController()).build();
Kotlin
client = WebTestClient.bindToController(TestController()).build()
The preceding example loads the WebFlux Java configuration and registers the given controller.
The resulting WebFlux application is tested without an HTTP server by using mock request and
response objects. There are more methods on the builder to customize the default WebFlux Java
configuration.
1.2. Bind to Router Function
The following example shows how to set up a server from a RouterFunction:
Java
RouterFunction<?> route = ...
client = WebTestClient.bindToRouterFunction(route).build();
Kotlin
val route: RouterFunction<*> = ...
val client = WebTestClient.bindToRouterFunction(route).build()
Internally, the configuration is passed to RouterFunctions.toWebHandler. The resulting WebFlux
application is tested without an HTTP server by using mock request and response objects.
1.3. Bind to ApplicationContext
The following example shows how to set up a server from the Spring configuration of your
application or some subset of it:
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Java
@SpringJUnitConfig(WebConfig.class) ①
class MyTests {
WebTestClient client;
@BeforeEach
void setUp(ApplicationContext context) { ②
client = WebTestClient.bindToApplicationContext(context).build(); ③
}
}
① Specify the configuration to load
② Inject the configuration
③ Create the WebTestClient
Kotlin
@SpringJUnitConfig(WebConfig::class) ①
class MyTests {
lateinit var client: WebTestClient
@BeforeEach
fun setUp(context: ApplicationContext) { ②
client = WebTestClient.bindToApplicationContext(context).build() ③
}
}
① Specify the configuration to load
② Inject the configuration
③ Create the WebTestClient
Internally, the configuration is passed to WebHttpHandlerBuilder to set up the request processing
chain. See WebHandler API for more details. The resulting WebFlux application is tested without an
HTTP server by using mock request and response objects.
1.4. Bind to Server
The following server setup option lets you connect to a running server:
Java
client = WebTestClient.bindToServer().baseUrl("http://localhost:8080").build();
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Kotlin
client = WebTestClient.bindToServer().baseUrl("http://localhost:8080").build()
1.5. Client Builder
In addition to the server setup options described earlier, you can also configure client options,
including base URL, default headers, client filters, and others. These options are readily available
following bindToServer. For all others, you need to use configureClient() to transition from server
to client configuration, as follows:
Java
client = WebTestClient.bindToController(new TestController())
.configureClient()
.baseUrl("/test")
.build();
Kotlin
client = WebTestClient.bindToController(TestController())
.configureClient()
.baseUrl("/test")
.build()
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Chapter 2. Writing Tests
WebTestClient provides an API identical to WebClient up to the point of performing a request by
using exchange(). What follows after exchange() is a chained API workflow to verify responses.
Typically, you start by asserting the response status and headers, as follows:
Java
client.get().uri("/persons/1")
.accept(MediaType.APPLICATION_JSON)
.exchange()
.expectStatus().isOk()
.expectHeader().contentType(MediaType.APPLICATION_JSON)
Kotlin
client.get().uri("/persons/1")
.accept(MediaType.APPLICATION_JSON)
.exchange()
.expectStatus().isOk()
.expectHeader().contentType(MediaType.APPLICATION_JSON)
Then you specify how to decode and consume the response body:
• expectBody(Class<T>): Decode to single object.
• expectBodyList(Class<T>): Decode and collect objects to List<T>.
• expectBody(): Decode to byte[] for JSON Content or an empty body.
Then you can use built-in assertions for the body. The following example shows one way to do so:
Java
client.get().uri("/persons")
.exchange()
.expectStatus().isOk()
.expectBodyList(Person.class).hasSize(3).contains(person);
Kotlin
import org.springframework.test.web.reactive.server.expectBodyList
client.get().uri("/persons")
.exchange()
.expectStatus().isOk()
.expectBodyList<Person>().hasSize(3).contains(person)
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You can also go beyond the built-in assertions and create your own, as the following example
shows:
Java
import org.springframework.test.web.reactive.server.expectBody
client.get().uri("/persons/1")
.exchange()
.expectStatus().isOk()
.expectBody(Person.class)
.consumeWith(result -> {
// custom assertions (e.g. AssertJ)...
});
Kotlin
client.get().uri("/persons/1")
.exchange()
.expectStatus().isOk()
.expectBody<Person>()
.consumeWith {
// custom assertions (e.g. AssertJ)...
}
You can also exit the workflow and get a result, as follows:
Java
EntityExchangeResult<Person> result = client.get().uri("/persons/1")
.exchange()
.expectStatus().isOk()
.expectBody(Person.class)
.returnResult();
Kotlin
import org.springframework.test.web.reactive.server.expectBody
val result = client.get().uri("/persons/1")
.exchange()
.expectStatus().isOk
.expectBody<Person>()
.returnResult()
When you need to decode to a target type with generics, look for the overloaded
methods that accept ParameterizedTypeReference instead of Class<T>.
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2.1. No Content
If the response has no content (or you do not care if it does) use Void.class, which ensures that
resources are released. The following example shows how to do so:
Java
client.get().uri("/persons/123")
.exchange()
.expectStatus().isNotFound()
.expectBody(Void.class);
Kotlin
client.get().uri("/persons/123")
.exchange()
.expectStatus().isNotFound
.expectBody<Unit>()
Alternatively, if you want to assert there is no response content, you can use code similar to the
following:
Java
client.post().uri("/persons")
.body(personMono, Person.class)
.exchange()
.expectStatus().isCreated()
.expectBody().isEmpty();
Kotlin
client.post().uri("/persons")
.bodyValue(person)
.exchange()
.expectStatus().isCreated()
.expectBody().isEmpty()
2.2. JSON Content
When you use expectBody(), the response is consumed as a byte[]. This is useful for raw content
assertions. For example, you can use JSONAssert to verify JSON content, as follows:
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Java
client.get().uri("/persons/1")
.exchange()
.expectStatus().isOk()
.expectBody()
.json("{\"name\":\"Jane\"}")
Kotlin
client.get().uri("/persons/1")
.exchange()
.expectStatus().isOk()
.expectBody()
.json("{\"name\":\"Jane\"}")
You can also use JSONPath expressions, as follows:
Java
client.get().uri("/persons")
.exchange()
.expectStatus().isOk()
.expectBody()
.jsonPath("$[0].name").isEqualTo("Jane")
.jsonPath("$[1].name").isEqualTo("Jason");
Kotlin
client.get().uri("/persons")
.exchange()
.expectStatus().isOk()
.expectBody()
.jsonPath("$[0].name").isEqualTo("Jane")
.jsonPath("$[1].name").isEqualTo("Jason")
2.3. Streaming Responses
To test infinite streams (for example, "text/event-stream" or "application/stream+json"), you need
to exit the chained API (by using returnResult), immediately after the response status and header
assertions, as the following example shows:
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Java
FluxExchangeResult<MyEvent> result = client.get().uri("/events")
.accept(TEXT_EVENT_STREAM)
.exchange()
.expectStatus().isOk()
.returnResult(MyEvent.class);
Kotlin
import org.springframework.test.web.reactive.server.returnResult
val result = client.get().uri("/events")
.accept(TEXT_EVENT_STREAM)
.exchange()
.expectStatus().isOk()
.returnResult<MyEvent>()
Now you can consume the Flux<T>, assert decoded objects as they come, and then cancel at some
point when test objectives are met. We recommend using the StepVerifier from the reactor-test
module to do that, as the following example shows:
Java
Flux<Event> eventFlux = result.getResponseBody();
StepVerifier.create(eventFlux)
.expectNext(person)
.expectNextCount(4)
.consumeNextWith(p -> ...)
.thenCancel()
.verify();
Kotlin
val eventFlux = result.getResponseBody()
StepVerifier.create(eventFlux)
.expectNext(person)
.expectNextCount(4)
.consumeNextWith { p -> ... }
.thenCancel()
.verify()
2.4. Request Body
When it comes to building requests, the WebTestClient offers an API identical to the WebClient, and
the implementation is mostly a simple pass-through. See the WebClient documentation for
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examples on how to prepare a request with a body, including submitting form data, multipart
requests, and more.
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