Improve documentation for WebTestClient

Closes gh-11203

spring-boot-project/spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -5907,9 +5907,16 @@ running server, as shown in the following example:
 
 [source,java,indent=0]
 ----
-include::{code-examples}/test/web/RandomPortExampleTests.java[tag=test-random-port]
+include::{code-examples}/test/web/RandomPortTestRestTemplateExampleTests.java[tag=test-random-port]
 ----
 
+If you prefer to use a {spring-reference}testing.html#webtestclient[`WebTestClient`], you
+can use that as well:
+
+[source,java,indent=0]
+----
+include::{code-examples}/test/web/RandomPortWebTestClientExampleTests.java[tag=test-random-port]
+----
 
 
 [[boot-features-testing-spring-boot-applications-mocking-beans]]
@@ -6194,8 +6201,10 @@ additional configuration classes using `@Import` on your test.
 Often, `@WebFluxTest` is limited to a single controller and used in combination with the
 `@MockBean` annotation to provide mock implementations for required collaborators.
 
-`@WebFluxTest` also auto-configures `WebTestClient`, which offers a powerful way to
-quickly test WebFlux controllers without needing to start a full HTTP server.
+`@WebFluxTest` also auto-configures
+{spring-reference}testing.html#webtestclient[`WebTestClient`]`WebTestClient`, which offers
+a powerful way to quickly test WebFlux controllers without needing to start a full HTTP
+server.
 
 TIP: You can also auto-configure `WebTestClient` in a non-`@WebFluxTest` (such as
 `@SpringBootTest`) by annotating it with `@AutoConfigureWebTestClient`. The following

spring-boot-project/spring-boot-docs/src/main/java/org/springframework/boot/test/web/RandomPortTestRestTemplateExampleTests.java

@@ -30,7 +30,7 @@ import static org.assertj.core.api.Assertions.assertThat;
 
 @RunWith(SpringRunner.class)
 @SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
-public class RandomPortExampleTests {
+public class RandomPortTestRestTemplateExampleTests {
 
 	@Autowired
 	private TestRestTemplate restTemplate;

spring-boot-project/spring-boot-docs/src/main/java/org/springframework/boot/test/web/RandomPortWebTestClientExampleTests.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2012-2018 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.test.web;
+
+// tag::test-random-port[]
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
+import org.springframework.test.context.junit4.SpringRunner;
+import org.springframework.test.web.reactive.server.WebTestClient;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
+public class RandomPortWebTestClientExampleTests {
+
+	@Autowired
+	private WebTestClient webClient;
+
+	@Test
+	public void exampleTest() {
+		this.webClient.get()
+				.uri("/")
+				.exchange()
+				.expectStatus().isOk()
+				.expectBody(String.class).isEqualTo("Hello World");
+	}
+
+}
+// tag::test-random-port[]