Add Kotlin code snippets to WebTestClient testing refdoc

Closes gh-21778

src/docs/asciidoc/testing-webtestclient.adoc

@@ -27,11 +27,16 @@ a URL to connect to a running server.
 
 The following example shows how to create a server setup to test one `@Controller` at a time:
 
-[source,java,intent=0]
+[source,java,indent=0,subs="verbatim,quotes",role="primary"]
-[subs="verbatim,quotes"]
+.Java
 ----
 	client = WebTestClient.bindToController(new TestController()).build();
 ----
+[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
+.Kotlin
+----
+	client = WebTestClient.bindToController(TestController()).build()
+----
 
 The preceding example loads the <<web-reactive.adoc#webflux-config, WebFlux Java configuration>>
 and registers the given controller. The resulting WebFlux application is tested
@@ -46,12 +51,18 @@ on the builder to customize the default WebFlux Java configuration.
 The following example shows how to set up a server from a
 <<web-reactive.adoc#webflux-fn, RouterFunction>>:
 
-[source,java,intent=0]
+[source,java,indent=0,subs="verbatim,quotes",role="primary"]
-[subs="verbatim,quotes"]
+.Java
 ----
 	RouterFunction<?> route = ...
 	client = WebTestClient.bindToRouterFunction(route).build();
 ----
+[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
+.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
@@ -65,11 +76,10 @@ request and response objects.
 The following example shows how to setup a server from the Spring configuration of your application or
 some subset of it:
 
-[source,java,intent=0]
+[source,java,indent=0,subs="verbatim,quotes",role="primary"]
-[subs="verbatim,quotes"]
+.Java
 ----
-	@RunWith(SpringRunner.class)
+	@SpringJUnitConfig(WebConfig.class) // <1>
-	@ContextConfiguration(classes = WebConfig.class) // <1>
 	public class MyTests {
 
 		@Autowired
@@ -77,13 +87,33 @@ some subset of it:
 
 		private WebTestClient client;
 
-		@Before
+		@BeforeEach
 		public void setUp() {
 			client = WebTestClient.bindToApplicationContext(context).build(); // <3>
 		}
 	}
 ----
+<1> Specify the configuration to load
+<2> Inject the configuration
+<3> Create the `WebTestClient`
+
+[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
+.Kotlin
+----
+	@SpringJUnitConfig(WebConfig::class) // <1>
+	class MyTests {
 
+		@Autowired
+		lateinit var context: ApplicationContext // <2>
+
+		lateinit var client: WebTestClient
+
+		@BeforeEach
+		fun setUp() {
+			client = WebTestClient.bindToApplicationContext(context).build() // <3>
+		}
+	}
+----
 <1> Specify the configuration to load
 <2> Inject the configuration
 <3> Create the `WebTestClient`
@@ -100,11 +130,16 @@ using mock request and response objects.
 
 The following server setup option lets you connect to a running server:
 
-[source,java,intent=0]
+[source,java,indent=0,subs="verbatim,quotes",role="primary"]
-[subs="verbatim,quotes"]
+.Java
 ----
 	client = WebTestClient.bindToServer().baseUrl("http://localhost:8080").build();
 ----
+[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
+.Kotlin
+----
+	client = WebTestClient.bindToServer().baseUrl("http://localhost:8080").build()
+----
 
 
 
@@ -116,14 +151,22 @@ options, including base URL, default headers, client filters, and others. These
 are readily available following `bindToServer`. For all others, you need to use
 `configureClient()` to transition from server to client configuration, as follows:
 
-[source,java,intent=0]
+[source,java,indent=0,subs="verbatim,quotes",role="primary"]
-[subs="verbatim,quotes"]
+.Java
 ----
 	client = WebTestClient.bindToController(new TestController())
 			.configureClient()
 			.baseUrl("/test")
 			.build();
 ----
+[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
+.Kotlin
+----
+	client = WebTestClient.bindToController(TestController())
+			.configureClient()
+			.baseUrl("/test")
+			.build()
+----
 
 
 
@@ -137,15 +180,23 @@ up to the point of performing a request by using `exchange()`. What follows afte
 
 Typically, you start by asserting the response status and headers, as follows:
 
-[source,java,intent=0]
+[source,java,indent=0,subs="verbatim,quotes",role="primary"]
-[subs="verbatim,quotes"]
+.Java
+----
+	client.get().uri("/persons/1")
+				.accept(MediaType.APPLICATION_JSON)
+				.exchange()
+				.expectStatus().isOk()
+				.expectHeader().contentType(MediaType.APPLICATION_JSON)
+----
+[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
+.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:
@@ -156,18 +207,32 @@ Then you specify how to decode and consume the response body:
 
 Then you can use built-in assertions for the body. The following example shows one way to do so:
 
-[source,java,intent=0]
+[source,java,indent=0,subs="verbatim,quotes",role="primary"]
-[subs="verbatim,quotes"]
+.Java
 ----
 	client.get().uri("/persons")
 			.exchange()
 			.expectStatus().isOk()
 			.expectBodyList(Person.class).hasSize(3).contains(person);
 ----
+[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
+.Kotlin
+----
+	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:
 
+[source,java,indent=0,subs="verbatim,quotes",role="primary"]
+.Java
 ----
+    import org.springframework.test.web.reactive.server.expectBody
+
 	client.get().uri("/persons/1")
 			.exchange()
 			.expectStatus().isOk()
@@ -176,9 +241,22 @@ You can also go beyond the built-in assertions and create your own, as the follo
 				// custom assertions (e.g. AssertJ)...
 			});
 ----
+[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
+.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:
 
+[source,java,indent=0,subs="verbatim,quotes",role="primary"]
+.Java
 ----
 	EntityExchangeResult<Person> result = client.get().uri("/persons/1")
 			.exchange()
@@ -186,6 +264,17 @@ You can also exit the workflow and get a result, as follows:
 			.expectBody(Person.class)
 			.returnResult();
 ----
+[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
+.Kotlin
+----
+	import org.springframework.test.web.reactive.server.expectBody
+
+	val result = client.get().uri("/persons/1")
+			.exchange()
+			.expectStatus().isOk
+			.expectBody<Person>()
+			.returnResult()
+----
 
 TIP: When you need to decode to a target type with generics, look for the overloaded methods
 that accept
@@ -200,19 +289,27 @@ instead of `Class<T>`.
 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:
 
-[source,java,intent=0]
+[source,java,indent=0,subs="verbatim,quotes",role="primary"]
-[subs="verbatim,quotes"]
+.Java
 ----
 	client.get().uri("/persons/123")
 			.exchange()
 			.expectStatus().isNotFound()
 			.expectBody(Void.class);
 ----
+[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
+.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:
 
-[source,java,intent=0]
+[source,java,indent=0,subs="verbatim,quotes",role="primary"]
-[subs="verbatim,quotes"]
+.Java
 ----
 	client.post().uri("/persons")
 			.body(personMono, Person.class)
@@ -220,7 +317,15 @@ Alternatively, if you want to assert there is no response content, you can use c
 			.expectStatus().isCreated()
 			.expectBody().isEmpty();
 ----
-
+[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
+.Kotlin
+----
+	client.post().uri("/persons")
+	.bodyValue(person)
+	.exchange()
+	.expectStatus().isCreated()
+	.expectBody().isEmpty()
+----
 
 
 [[webtestclient-json]]
@@ -230,8 +335,17 @@ When you use `expectBody()`, the response is consumed as a `byte[]`. This is use
 raw content assertions. For example, you can use
 https://jsonassert.skyscreamer.org[JSONAssert] to verify JSON content, as follows:
 
-[source,java,intent=0]
+[source,java,indent=0,subs="verbatim,quotes",role="primary"]
-[subs="verbatim,quotes"]
+.Java
+----
+	client.get().uri("/persons/1")
+			.exchange()
+			.expectStatus().isOk()
+			.expectBody()
+			.json("{\"name\":\"Jane\"}")
+----
+[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
+.Kotlin
 ----
 	client.get().uri("/persons/1")
 			.exchange()
@@ -242,8 +356,8 @@ https://jsonassert.skyscreamer.org[JSONAssert] to verify JSON content, as follow
 
 You can also use https://github.com/jayway/JsonPath[JSONPath] expressions, as follows:
 
-[source,java,intent=0]
+[source,java,indent=0,subs="verbatim,quotes",role="primary"]
-[subs="verbatim,quotes"]
+.Java
 ----
 	client.get().uri("/persons")
 			.exchange()
@@ -252,6 +366,16 @@ You can also use https://github.com/jayway/JsonPath[JSONPath] expressions, as fo
 			.jsonPath("$[0].name").isEqualTo("Jane")
 			.jsonPath("$[1].name").isEqualTo("Jason");
 ----
+[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
+.Kotlin
+----
+	client.get().uri("/persons")
+			.exchange()
+			.expectStatus().isOk()
+			.expectBody()
+			.jsonPath("$[0].name").isEqualTo("Jane")
+			.jsonPath("$[1].name").isEqualTo("Jason")
+----
 
 
 
@@ -262,8 +386,8 @@ To test infinite streams (for example, `"text/event-stream"` or `"application/st
 you need to exit the chained API (by using `returnResult`), immediately after the response status
 and header assertions, as the following example shows:
 
-[source,java,intent=0]
+[source,java,indent=0,subs="verbatim,quotes",role="primary"]
-[subs="verbatim,quotes"]
+.Java
 ----
 	FluxExchangeResult<MyEvent> result = client.get().uri("/events")
 			.accept(TEXT_EVENT_STREAM)
@@ -272,15 +396,26 @@ and header assertions, as the following example shows:
 			.returnResult(MyEvent.class);
 
 ----
+[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
+.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:
 
-[source,java,intent=0]
+[source,java,indent=0,subs="verbatim,quotes",role="primary"]
-[subs="verbatim,quotes"]
+.Java
 ----
-	Flux<Event> eventFux = result.getResponseBody();
+	Flux<Event> eventFlux = result.getResponseBody();
 
 	StepVerifier.create(eventFlux)
 			.expectNext(person)
@@ -289,6 +424,18 @@ from the `reactor-test` module to do that, as the following example shows:
 			.thenCancel()
 			.verify();
 ----
+[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
+.Kotlin
+----
+	val eventFlux = result.getResponseBody()
+
+	StepVerifier.create(eventFlux)
+			.expectNext(person)
+			.expectNextCount(4)
+			.consumeNextWith { p -> ... }
+			.thenCancel()
+			.verify()
+----