WebTestClient
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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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.
Bind to Controller
The following example shows how to create a server setup to test one @Controller
at a time:
client = WebTestClient.bindToController(new TestController()).build();
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.
Bind to Router Function
The following example shows how to set up a server from a RouterFunction:
RouterFunction<?> route = ...
client = WebTestClient.bindToRouterFunction(route).build();
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.
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:
@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 |
@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.
Bind to Server
The following server setup option lets you connect to a running server:
client = WebTestClient.bindToServer().baseUrl("http://localhost:8080").build();
client = WebTestClient.bindToServer().baseUrl("http://localhost:8080").build()
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:
client = WebTestClient.bindToController(new TestController())
.configureClient()
.baseUrl("/test")
.build();
client = WebTestClient.bindToController(TestController())
.configureClient()
.baseUrl("/test")
.build()
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:
client.get().uri("/persons/1")
.accept(MediaType.APPLICATION_JSON)
.exchange()
.expectStatus().isOk()
.expectHeader().contentType(MediaType.APPLICATION_JSON)
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 toList<T>
. -
expectBody()
: Decode tobyte[]
for webtestclient-json or an empty body.
Then you can use built-in assertions for the body. The following example shows one way to do so:
client.get().uri("/persons")
.exchange()
.expectStatus().isOk()
.expectBodyList(Person.class).hasSize(3).contains(person);
import org.springframework.test.web.reactive.server.expectBodyList
client.get().uri("/persons")
.exchange()
.expectStatus().isOk()
.expectBodyList<Person>().hasSize(3).contains(person)
You can also go beyond the built-in assertions and create your own, as the following example shows:
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)...
});
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:
EntityExchangeResult<Person> result = client.get().uri("/persons/1")
.exchange()
.expectStatus().isOk()
.expectBody(Person.class)
.returnResult();
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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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:
client.get().uri("/persons/123")
.exchange()
.expectStatus().isNotFound()
.expectBody(Void.class);
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:
client.post().uri("/persons")
.body(personMono, Person.class)
.exchange()
.expectStatus().isCreated()
.expectBody().isEmpty();
client.post().uri("/persons")
.bodyValue(person)
.exchange()
.expectStatus().isCreated()
.expectBody().isEmpty()
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:
client.get().uri("/persons/1")
.exchange()
.expectStatus().isOk()
.expectBody()
.json("{\"name\":\"Jane\"}")
client.get().uri("/persons/1")
.exchange()
.expectStatus().isOk()
.expectBody()
.json("{\"name\":\"Jane\"}")
You can also use JSONPath expressions, as follows:
client.get().uri("/persons")
.exchange()
.expectStatus().isOk()
.expectBody()
.jsonPath("$[0].name").isEqualTo("Jane")
.jsonPath("$[1].name").isEqualTo("Jason");
client.get().uri("/persons")
.exchange()
.expectStatus().isOk()
.expectBody()
.jsonPath("$[0].name").isEqualTo("Jane")
.jsonPath("$[1].name").isEqualTo("Jason")
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:
FluxExchangeResult<MyEvent> result = client.get().uri("/events")
.accept(TEXT_EVENT_STREAM)
.exchange()
.expectStatus().isOk()
.returnResult(MyEvent.class);
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:
Flux<Event> eventFlux = result.getResponseBody();
StepVerifier.create(eventFlux)
.expectNext(person)
.expectNextCount(4)
.consumeNextWith(p -> ...)
.thenCancel()
.verify();
val eventFlux = result.getResponseBody()
StepVerifier.create(eventFlux)
.expectNext(person)
.expectNextCount(4)
.consumeNextWith { p -> ... }
.thenCancel()
.verify()
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 examples on
how to prepare a request with a body, including submitting form data, multipart requests,
and more.