Add support for RestTestClient

This commit adds support for RestTestClient for MockMvc and integration
tests.

Closes gh-47335

documentation/spring-boot-docs/src/docs/antora/modules/reference/pages/testing/spring-boot-applications.adoc

@@ -141,10 +141,11 @@ include-code::MyApplicationArgumentTests[]
 By default, javadoc:org.springframework.boot.test.context.SpringBootTest[format=annotation] does not start the server but instead sets up a mock environment for testing web endpoints.
 
 With Spring MVC, we can query our web endpoints using {url-spring-framework-docs}/testing/mockmvc.html[`MockMvc`].
-Three integrations are available:
+The following integrations are available:
 
 * The regular {url-spring-framework-docs}/testing/mockmvc/hamcrest.html[`MockMvc`] that uses Hamcrest.
 * {url-spring-framework-docs}/testing/mockmvc/assertj.html[`MockMvcTester`] that wraps javadoc:org.springframework.test.web.servlet.MockMvc[] and uses AssertJ.
+* {url-spring-framework-docs}/testing/resttestclient.html[`RestTestClient`] where javadoc:org.springframework.test.web.servlet.MockMvc[] is plugged in as the server to handle requests with.
 * {url-spring-framework-docs}/testing/webtestclient.html[`WebTestClient`] where javadoc:org.springframework.test.web.servlet.MockMvc[] is plugged in as the server to handle requests with.
 
 The following example showcases the available integrations:
@@ -176,19 +177,32 @@ If you need to start a full running server, we recommend that you use random por
 If you use `@SpringBootTest(webEnvironment=WebEnvironment.RANDOM_PORT)`, an available port is picked at random each time your test runs.
 
 The javadoc:org.springframework.boot.test.web.server.LocalServerPort[format=annotation] annotation can be used to xref:how-to:webserver.adoc#howto.webserver.discover-port[inject the actual port used] into your test.
-For convenience, tests that need to make REST calls to the started server can additionally autowire a {url-spring-framework-docs}/testing/webtestclient.html[`WebTestClient`], which resolves relative links to the running server and comes with a dedicated API for verifying responses, as shown in the following example:
+
+For convenience, tests that need to make REST calls to the started server can additionally autowire a
+{url-spring-framework-docs}/testing/resttestclient.html[`RestTestClient`] which resolves relative links to the running server and comes with a dedicated API for verifying responses, as shown in the following example:
+
+include-code::MyRandomPortRestTestClientTests[]
+
+If you have `spring-webflux` on the classpath, you can also autowire a {url-spring-framework-docs}/testing/webtestclient.html[`WebTestClient`] that provides a similar API:
 
 include-code::MyRandomPortWebTestClientTests[]
 
 TIP: javadoc:org.springframework.test.web.reactive.server.WebTestClient[] can also used with a xref:testing/spring-boot-applications.adoc#testing.spring-boot-applications.with-mock-environment[mock environment], removing the need for a running server, by annotating your test class with javadoc:org.springframework.boot.webflux.test.autoconfigure.AutoConfigureWebTestClient[format=annotation] from `spring-boot-webflux-test`.
 
-This setup requires `spring-webflux` on the classpath.
-If you can not or will not add webflux, the `spring-boot-web-server-test` modules provides a javadoc:org.springframework.boot.web.server.test.client.TestRestTemplate[] facility:
+The `spring-boot-web-server-test` modules also provides a javadoc:org.springframework.boot.web.server.test.client.TestRestTemplate[] facility:
 
 include-code::MyRandomPortTestRestTemplateTests[]
 
 
 
+[[testing.spring-boot-applications.customizing-rest-test-client]]
+== Customizing RestTestClient
+
+To customize the javadoc:org.springframework.test.web.servlet.client.RestTestClient[] bean, configure a javadoc:org.springframework.boot.web.server.test.client.RestTestClientBuilderCustomizer[] bean.
+Any such beans are called with the javadoc:org.springframework.test.web.servlet.client.RestTestClient$Builder[] that is used to create the javadoc:org.springframework.test.web.servlet.client.RestTestClient[].
+
+
+
 [[testing.spring-boot-applications.customizing-web-test-client]]
 == Customizing WebTestClient
 

documentation/spring-boot-docs/src/docs/antora/modules/reference/pages/testing/test-utilities.adoc

@@ -48,8 +48,9 @@ In either case, the template is fault tolerant.
 This means that it behaves in a test-friendly way by not throwing exceptions on 4xx and 5xx errors.
 Instead, such errors can be detected through the returned javadoc:org.springframework.http.ResponseEntity[] and its status code.
 
-TIP: Spring Framework 5.0 provides a new javadoc:org.springframework.test.web.reactive.server.WebTestClient[] that works for xref:testing/spring-boot-applications.adoc#testing.spring-boot-applications.spring-webflux-tests[WebFlux integration tests] and both xref:testing/spring-boot-applications.adoc#testing.spring-boot-applications.with-running-server[WebFlux and MVC end-to-end testing].
-It provides a fluent API for assertions, unlike javadoc:org.springframework.boot.test.web.client.TestRestTemplate[].
+If you need fluent API for assertions, consider using javadoc:org.springframework.test.web.servlet.client.RestTestClient[] that works with xref:testing/spring-boot-applications.adoc#testing.spring-boot-applications.with-mock-environment[mock environments] and xref:testing/spring-boot-applications.adoc#testing.spring-boot-applications.with-running-server[end-to-end tests].
+
+If you are using Spring WebFlux, consider the javadoc:org.springframework.test.web.reactive.server.WebTestClient[] that provides a similar API and works with xref:testing/spring-boot-applications.adoc#testing.spring-boot-applications.with-mock-environment[mock environments], xref:testing/spring-boot-applications.adoc#testing.spring-boot-applications.spring-webflux-tests[WebFlux integration tests], and xref:testing/spring-boot-applications.adoc#testing.spring-boot-applications.with-running-server[end-to-end tests].
 
 It is recommended, but not mandatory, to use the Apache HTTP Client (version 5.1 or better).
 If you have that on your classpath, the javadoc:org.springframework.boot.test.web.client.TestRestTemplate[] responds by configuring the client appropriately.

documentation/spring-boot-docs/src/main/java/org/springframework/boot/docs/testing/springbootapplications/withmockenvironment/MyMockMvcTests.java

@@ -24,6 +24,7 @@ import org.springframework.boot.webmvc.test.autoconfigure.AutoConfigureMockMvc;
 import org.springframework.test.web.reactive.server.WebTestClient;
 import org.springframework.test.web.servlet.MockMvc;
 import org.springframework.test.web.servlet.assertj.MockMvcTester;
+import org.springframework.test.web.servlet.client.RestTestClient;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
@@ -45,6 +46,17 @@ class MyMockMvcTests {
 		assertThat(mvc.get().uri("/")).hasStatusOk().hasBodyTextEqualTo("Hello World");
 	}
 
+	@Test
+	void testWithRestTestClient(@Autowired RestTestClient webClient) {
+		// @formatter:off
+		webClient
+				.get().uri("/")
+				.exchange()
+				.expectStatus().isOk()
+				.expectBody(String.class).isEqualTo("Hello World");
+		// @formatter:on
+	}
+
 	// If Spring WebFlux is on the classpath, you can drive MVC tests with a WebTestClient
 	@Test
 	void testWithWebTestClient(@Autowired WebTestClient webClient) {

documentation/spring-boot-docs/src/main/java/org/springframework/boot/docs/testing/springbootapplications/withrunningserver/MyRandomPortRestTestClientTests.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2012-present 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
+ *
+ *      https://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.docs.testing.springbootapplications.withrunningserver;
+
+import org.junit.jupiter.api.Test;
+
+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.web.servlet.client.RestTestClient;
+
+@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
+class MyRandomPortRestTestClientTests {
+
+	@Test
+	void exampleTest(@Autowired RestTestClient webClient) {
+		// @formatter:off
+		webClient
+			.get().uri("/")
+			.exchange()
+			.expectStatus().isOk()
+			.expectBody(String.class).isEqualTo("Hello World");
+		// @formatter:on
+	}
+
+}

module/spring-boot-restclient/src/main/java/org/springframework/boot/restclient/RootUriBuilderFactory.java

@@ -31,7 +31,12 @@ import org.springframework.web.util.UriTemplateHandler;
  */
 public class RootUriBuilderFactory extends RootUriTemplateHandler implements UriBuilderFactory {
 
-	RootUriBuilderFactory(String rootUri, UriTemplateHandler delegate) {
+	/**
+	 * Create an instance with the root URI to use.
+	 * @param rootUri the root URI
+	 * @param delegate the {@link UriTemplateHandler} to delegate to
+	 */
+	public RootUriBuilderFactory(String rootUri, UriTemplateHandler delegate) {
 		super(rootUri, delegate);
 	}
 

module/spring-boot-web-server-test/src/main/java/org/springframework/boot/web/server/test/client/RestTestClientBuilderCustomizer.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2012-present 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
+ *
+ *      https://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.web.server.test.client;
+
+import org.springframework.test.web.servlet.client.RestTestClient;
+
+/**
+ * A customizer that can be implemented by beans wishing to customize the
+ * {@link RestTestClient.Builder} to fine-tine its auto-configuration before a
+ * {@link RestTestClient} is created.
+ *
+ * @author Stephane Nicoll
+ * @since 4.0.0
+ */
+@FunctionalInterface
+public interface RestTestClientBuilderCustomizer {
+
+	/**
+	 * Customize the given {@link RestTestClient.Builder Builder}.
+	 * @param builder the builder
+	 */
+	void customize(RestTestClient.Builder<?> builder);
+
+}

module/spring-boot-web-server-test/src/main/java/org/springframework/boot/web/server/test/client/RestTestClientContextCustomizer.java

@@ -0,0 +1,194 @@
+/*
+ * Copyright 2012-present 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
+ *
+ *      https://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.web.server.test.client;
+
+import org.jspecify.annotations.Nullable;
+
+import org.springframework.aot.AotDetector;
+import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.BeanFactory;
+import org.springframework.beans.factory.BeanFactoryAware;
+import org.springframework.beans.factory.BeanFactoryUtils;
+import org.springframework.beans.factory.FactoryBean;
+import org.springframework.beans.factory.ListableBeanFactory;
+import org.springframework.beans.factory.NoSuchBeanDefinitionException;
+import org.springframework.beans.factory.config.BeanDefinition;
+import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
+import org.springframework.beans.factory.support.BeanDefinitionRegistry;
+import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;
+import org.springframework.beans.factory.support.RootBeanDefinition;
+import org.springframework.boot.restclient.RootUriBuilderFactory;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.web.server.reactive.AbstractReactiveWebServerFactory;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.ApplicationContextAware;
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.context.annotation.ConfigurationClassPostProcessor;
+import org.springframework.core.Ordered;
+import org.springframework.test.context.ContextCustomizer;
+import org.springframework.test.context.MergedContextConfiguration;
+import org.springframework.test.context.TestContextAnnotationUtils;
+import org.springframework.test.web.servlet.client.RestTestClient;
+import org.springframework.util.Assert;
+
+/**
+ * {@link ContextCustomizer} for {@link RestTestClient}.
+ *
+ * @author Stephane Nicoll
+ */
+class RestTestClientContextCustomizer implements ContextCustomizer {
+
+	@Override
+	public void customizeContext(ConfigurableApplicationContext context, MergedContextConfiguration mergedConfig) {
+		if (AotDetector.useGeneratedArtifacts()) {
+			return;
+		}
+		SpringBootTest springBootTest = TestContextAnnotationUtils.findMergedAnnotation(mergedConfig.getTestClass(),
+				SpringBootTest.class);
+		Assert.state(springBootTest != null, "'springBootTest' must not be null");
+		if (springBootTest.webEnvironment().isEmbedded()) {
+			registerRestTestClient(context);
+		}
+	}
+
+	private void registerRestTestClient(ConfigurableApplicationContext context) {
+		ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
+		if (beanFactory instanceof BeanDefinitionRegistry registry) {
+			registerRestTestClient(registry);
+		}
+	}
+
+	private void registerRestTestClient(BeanDefinitionRegistry registry) {
+		RootBeanDefinition definition = new RootBeanDefinition(RestTestClientRegistrar.class);
+		definition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
+		registry.registerBeanDefinition(RestTestClientRegistrar.class.getName(), definition);
+	}
+
+	@Override
+	public boolean equals(@Nullable Object obj) {
+		return (obj != null) && (obj.getClass() == getClass());
+	}
+
+	@Override
+	public int hashCode() {
+		return getClass().hashCode();
+	}
+
+	/**
+	 * {@link BeanDefinitionRegistryPostProcessor} that runs after the
+	 * {@link ConfigurationClassPostProcessor} and add a {@link RestTestClientFactory}
+	 * bean definition when a {@link RestTestClient} hasn't already been registered.
+	 */
+	static class RestTestClientRegistrar implements BeanDefinitionRegistryPostProcessor, Ordered, BeanFactoryAware {
+
+		@SuppressWarnings("NullAway.Init")
+		private BeanFactory beanFactory;
+
+		@Override
+		public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
+			this.beanFactory = beanFactory;
+		}
+
+		@Override
+		public int getOrder() {
+			return Ordered.LOWEST_PRECEDENCE;
+		}
+
+		@Override
+		public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
+			if (AotDetector.useGeneratedArtifacts()) {
+				return;
+			}
+			if (BeanFactoryUtils.beanNamesForTypeIncludingAncestors((ListableBeanFactory) this.beanFactory,
+					RestTestClient.class, false, false).length == 0) {
+				registry.registerBeanDefinition(RestTestClient.class.getName(),
+						new RootBeanDefinition(RestTestClientFactory.class));
+			}
+
+		}
+
+		@Override
+		public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
+		}
+
+	}
+
+	/**
+	 * {@link FactoryBean} used to create and configure a {@link RestTestClient}.
+	 */
+	public static class RestTestClientFactory implements FactoryBean<RestTestClient>, ApplicationContextAware {
+
+		@SuppressWarnings("NullAway.Init")
+		private ApplicationContext applicationContext;
+
+		private @Nullable RestTestClient object;
+
+		@Override
+		public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
+			this.applicationContext = applicationContext;
+		}
+
+		@Override
+		public boolean isSingleton() {
+			return true;
+		}
+
+		@Override
+		public Class<?> getObjectType() {
+			return RestTestClient.class;
+		}
+
+		@Override
+		public RestTestClient getObject() {
+			if (this.object == null) {
+				this.object = createRestTestClient();
+			}
+			return this.object;
+		}
+
+		private RestTestClient createRestTestClient() {
+			boolean sslEnabled = isSslEnabled(this.applicationContext);
+			LocalHostUriTemplateHandler handler = new LocalHostUriTemplateHandler(
+					this.applicationContext.getEnvironment(), sslEnabled ? "https" : "http");
+			RestTestClient.Builder<?> builder = RestTestClient.bindToServer();
+			customizeRestTestClientBuilder(builder, this.applicationContext);
+			return builder.uriBuilderFactory(new RootUriBuilderFactory(handler.getRootUri(), handler)).build();
+		}
+
+		private boolean isSslEnabled(ApplicationContext context) {
+			try {
+				AbstractReactiveWebServerFactory webServerFactory = context
+					.getBean(AbstractReactiveWebServerFactory.class);
+				return webServerFactory.getSsl() != null && webServerFactory.getSsl().isEnabled();
+			}
+			catch (NoSuchBeanDefinitionException ex) {
+				return false;
+			}
+		}
+
+		private void customizeRestTestClientBuilder(RestTestClient.Builder<?> clientBuilder,
+				ApplicationContext context) {
+			for (RestTestClientBuilderCustomizer customizer : context
+				.getBeansOfType(RestTestClientBuilderCustomizer.class)
+				.values()) {
+				customizer.customize(clientBuilder);
+			}
+		}
+
+	}
+
+}

module/spring-boot-web-server-test/src/main/java/org/springframework/boot/web/server/test/client/RestTestClientContextCustomizerFactory.java

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2012-present 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
+ *
+ *      https://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.web.server.test.client;
+
+import java.util.List;
+
+import org.jspecify.annotations.Nullable;
+
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.ContextConfigurationAttributes;
+import org.springframework.test.context.ContextCustomizer;
+import org.springframework.test.context.ContextCustomizerFactory;
+import org.springframework.test.context.TestContextAnnotationUtils;
+import org.springframework.util.ClassUtils;
+
+/**
+ * {@link ContextCustomizerFactory} for {@code RestTestClient}.
+ *
+ * @author Stephane Nicoll
+ */
+class RestTestClientContextCustomizerFactory implements ContextCustomizerFactory {
+
+	private static final boolean restClientPresent;
+
+	static {
+		ClassLoader loader = RestTestClientContextCustomizerFactory.class.getClassLoader();
+		restClientPresent = ClassUtils.isPresent("org.springframework.web.client.RestClient", loader);
+	}
+
+	@Override
+	public @Nullable ContextCustomizer createContextCustomizer(Class<?> testClass,
+			List<ContextConfigurationAttributes> configAttributes) {
+		SpringBootTest springBootTest = TestContextAnnotationUtils.findMergedAnnotation(testClass,
+				SpringBootTest.class);
+		return (springBootTest != null && restClientPresent) ? new RestTestClientContextCustomizer() : null;
+	}
+
+}

module/spring-boot-web-server-test/src/main/resources/META-INF/spring.factories

@@ -4,6 +4,7 @@ org.springframework.boot.web.server.test.SpringBootTestRandomPortEnvironmentPost
 
 # Spring Test Context Customizer Factories
 org.springframework.test.context.ContextCustomizerFactory=\
+org.springframework.boot.web.server.test.client.RestTestClientContextCustomizerFactory,\
 org.springframework.boot.web.server.test.client.TestRestTemplateContextCustomizerFactory,\
 org.springframework.boot.web.server.test.client.reactive.WebTestClientContextCustomizerFactory,\
 org.springframework.boot.web.server.test.reactor.netty.DisableReactorResourceFactoryGlobalResourcesContextCustomizerFactory

module/spring-boot-web-server-test/src/test/java/org/springframework/boot/web/server/test/client/NoRestTestClientBeanChecker.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2012-present 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
+ *
+ *      https://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.web.server.test.client;
+
+import org.springframework.beans.factory.BeanFactory;
+import org.springframework.beans.factory.BeanFactoryAware;
+import org.springframework.beans.factory.BeanFactoryUtils;
+import org.springframework.beans.factory.ListableBeanFactory;
+import org.springframework.context.annotation.ImportSelector;
+import org.springframework.core.type.AnnotationMetadata;
+import org.springframework.test.web.servlet.client.RestTestClient;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * {@link ImportSelector} to check no {@link RestTestClient} definition is registered when
+ * config classes are processed.
+ */
+class NoRestTestClientBeanChecker implements ImportSelector, BeanFactoryAware {
+
+	@Override
+	public void setBeanFactory(BeanFactory beanFactory) {
+		assertThat(BeanFactoryUtils.beanNamesForTypeIncludingAncestors((ListableBeanFactory) beanFactory,
+				RestTestClient.class))
+			.isEmpty();
+	}
+
+	@Override
+	public String[] selectImports(AnnotationMetadata importingClassMetadata) {
+		return new String[0];
+	}
+
+}

module/spring-boot-web-server-test/src/test/java/org/springframework/boot/web/server/test/client/RestTestClientContextCustomizerIntegrationTests.java

@@ -0,0 +1,74 @@
+/*
+ * Copyright 2012-present 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
+ *
+ *      https://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.web.server.test.client;
+
+import org.junit.jupiter.api.Test;
+
+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.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Import;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.web.servlet.client.RestTestClient;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.BDDMockito.then;
+import static org.mockito.Mockito.mock;
+
+/**
+ * Integration test for {@link RestTestClientContextCustomizer}.
+ *
+ * @author Stephane Nicoll
+ */
+@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
+@DirtiesContext
+class RestTestClientContextCustomizerIntegrationTests {
+
+	@Autowired
+	private RestTestClient webClient;
+
+	@Autowired
+	private RestTestClientBuilderCustomizer clientBuilderCustomizer;
+
+	@Test
+	void test() {
+		then(this.clientBuilderCustomizer).should().customize(any(RestTestClient.Builder.class));
+		this.webClient.get().uri("/").exchange().expectBody(String.class).isEqualTo("hello");
+	}
+
+	@Configuration(proxyBeanMethods = false)
+	@Import({ TestWebMvcConfiguration.class, NoRestTestClientBeanChecker.class })
+	@RestController
+	static class TestConfig {
+
+		@GetMapping("/")
+		String root() {
+			return "hello";
+		}
+
+		@Bean
+		RestTestClientBuilderCustomizer clientBuilderCustomizer() {
+			return mock(RestTestClientBuilderCustomizer.class);
+		}
+
+	}
+
+}

module/spring-boot-web-server-test/src/test/java/org/springframework/boot/web/server/test/client/RestTestClientContextCustomizerTests.java

@@ -0,0 +1,92 @@
+/*
+ * Copyright 2012-present 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
+ *
+ *      https://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.web.server.test.client;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
+import org.springframework.beans.factory.support.DefaultListableBeanFactory;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
+import org.springframework.boot.test.context.runner.ApplicationContextRunner;
+import org.springframework.boot.web.server.test.client.RestTestClientContextCustomizer.RestTestClientRegistrar;
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.context.support.AbstractApplicationContext;
+import org.springframework.test.context.MergedContextConfiguration;
+import org.springframework.test.web.servlet.client.RestTestClient;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.BDDMockito.given;
+import static org.mockito.Mockito.mock;
+
+/**
+ * Tests for {@link RestTestClientContextCustomizer}.
+ *
+ * @author Moritz Halbritter
+ */
+class RestTestClientContextCustomizerTests {
+
+	@Test
+	void whenContextIsNotABeanDefinitionRegistryRestTestClientIsRegistered() {
+		new ApplicationContextRunner(TestApplicationContext::new)
+			.withInitializer(this::applyRestTestClientContextCustomizer)
+			.run((context) -> assertThat(context).hasSingleBean(RestTestClient.class));
+	}
+
+	@Test
+	void whenUsingAotGeneratedArtifactsRestTestClientIsNotRegistered() {
+		new ApplicationContextRunner().withSystemProperties("spring.aot.enabled:true")
+			.withInitializer(this::applyRestTestClientContextCustomizer)
+			.run((context) -> {
+				assertThat(context).doesNotHaveBean(RestTestClientRegistrar.class);
+				assertThat(context).doesNotHaveBean(RestTestClient.class);
+			});
+	}
+
+	@SuppressWarnings({ "unchecked", "rawtypes" })
+	void applyRestTestClientContextCustomizer(ConfigurableApplicationContext context) {
+		MergedContextConfiguration configuration = mock(MergedContextConfiguration.class);
+		given(configuration.getTestClass()).willReturn((Class) TestClass.class);
+		new RestTestClientContextCustomizer().customizeContext(context, configuration);
+	}
+
+	@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
+	static class TestClass {
+
+	}
+
+	static class TestApplicationContext extends AbstractApplicationContext {
+
+		private final ConfigurableListableBeanFactory beanFactory = new DefaultListableBeanFactory();
+
+		@Override
+		protected void refreshBeanFactory() {
+		}
+
+		@Override
+		protected void closeBeanFactory() {
+
+		}
+
+		@Override
+		public ConfigurableListableBeanFactory getBeanFactory() {
+			return this.beanFactory;
+		}
+
+	}
+
+}

module/spring-boot-web-server-test/src/test/java/org/springframework/boot/web/server/test/client/RestTestClientContextCustomizerWithCustomContextPathIntegrationTests.java

@@ -0,0 +1,88 @@
+/*
+ * Copyright 2012-present 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
+ *
+ *      https://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.web.server.test.client;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
+import org.springframework.boot.tomcat.servlet.TomcatServletWebServerFactory;
+import org.springframework.boot.web.server.servlet.ServletWebServerFactory;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Import;
+import org.springframework.context.support.PropertySourcesPlaceholderConfigurer;
+import org.springframework.test.context.TestPropertySource;
+import org.springframework.test.web.servlet.client.RestTestClient;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+import org.springframework.web.servlet.DispatcherServlet;
+
+/**
+ * Integration test for {@link RestTestClientContextCustomizer} with a custom context
+ * path.
+ *
+ * @author Stephane Nicoll
+ */
+@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
+@TestPropertySource(properties = "server.servlet.context-path=/test")
+class RestTestClientContextCustomizerWithCustomContextPathIntegrationTests {
+
+	@Autowired
+	private RestTestClient webClient;
+
+	@Test
+	void test() {
+		this.webClient.get().uri("/").exchange().expectBody(String.class).isEqualTo("hello");
+	}
+
+	@Configuration(proxyBeanMethods = false)
+	@Import(NoRestTestClientBeanChecker.class)
+	@RestController
+	static class TestConfig {
+
+		@Value("${server.port:8080}")
+		private int port = 8080;
+
+		@Bean
+		DispatcherServlet dispatcherServlet() {
+			return new DispatcherServlet();
+		}
+
+		@Bean
+		ServletWebServerFactory webServerFactory() {
+			TomcatServletWebServerFactory factory = new TomcatServletWebServerFactory();
+			factory.setPort(this.port);
+			factory.setContextPath("/test");
+			return factory;
+		}
+
+		@Bean
+		static PropertySourcesPlaceholderConfigurer propertyPlaceholder() {
+			return new PropertySourcesPlaceholderConfigurer();
+		}
+
+		@GetMapping("/")
+		String root() {
+			return "hello";
+		}
+
+	}
+
+}

module/spring-boot-web-server-test/src/test/java/org/springframework/boot/web/server/test/client/RestTestClientContextCustomizerWithOverridePathIntegrationTests.java

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2012-present 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
+ *
+ *      https://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.web.server.test.client;
+
+import org.junit.jupiter.api.Test;
+
+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.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Import;
+import org.springframework.test.web.servlet.client.RestTestClient;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.mock;
+
+/**
+ * Integration test for {@link RestTestClientContextCustomizer} with a custom client.
+ *
+ * @author Stephane Nicoll
+ */
+@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
+class RestTestClientContextCustomizerWithOverridePathIntegrationTests {
+
+	@Autowired
+	private RestTestClient webClient;
+
+	@Test
+	void test() {
+		assertThat(this.webClient).isInstanceOf(CustomRestTestClient.class);
+	}
+
+	@Configuration(proxyBeanMethods = false)
+	@Import({ TestWebMvcConfiguration.class, NoRestTestClientBeanChecker.class })
+	@RestController
+	static class TestConfig {
+
+		@GetMapping("/")
+		String root() {
+			return "hello";
+		}
+
+		@Bean
+		CustomRestTestClient customRestTestClient() {
+			return mock(CustomRestTestClient.class);
+		}
+
+	}
+
+	interface CustomRestTestClient extends RestTestClient {
+
+	}
+
+}

module/spring-boot-web-server-test/src/test/java/org/springframework/boot/web/server/test/client/TestWebMvcConfiguration.java

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2012-present 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
+ *
+ *      https://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.web.server.test.client;
+
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.boot.tomcat.servlet.TomcatServletWebServerFactory;
+import org.springframework.boot.web.server.servlet.ServletWebServerFactory;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.support.PropertySourcesPlaceholderConfigurer;
+import org.springframework.web.servlet.DispatcherServlet;
+import org.springframework.web.servlet.config.annotation.EnableWebMvc;
+
+@Configuration(proxyBeanMethods = false)
+@EnableWebMvc
+class TestWebMvcConfiguration {
+
+	@Value("${server.port:8080}")
+	private int port = 8080;
+
+	@Bean
+	DispatcherServlet dispatcherServlet() {
+		return new DispatcherServlet();
+	}
+
+	@Bean
+	ServletWebServerFactory webServerFactory() {
+		TomcatServletWebServerFactory factory = new TomcatServletWebServerFactory();
+		factory.setPort(this.port);
+		return factory;
+	}
+
+	@Bean
+	static PropertySourcesPlaceholderConfigurer propertyPlaceholder() {
+		return new PropertySourcesPlaceholderConfigurer();
+	}
+
+}

module/spring-boot-webmvc-test/src/main/java/org/springframework/boot/webmvc/test/autoconfigure/MockMvcAutoConfiguration.java

@@ -25,6 +25,7 @@ import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplicat
 import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication.Type;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.boot.web.server.autoconfigure.ServerProperties;
+import org.springframework.boot.web.server.test.client.RestTestClientBuilderCustomizer;
 import org.springframework.boot.web.server.test.client.reactive.WebTestClientBuilderCustomizer;
 import org.springframework.boot.webmvc.autoconfigure.DispatcherServletPath;
 import org.springframework.boot.webmvc.autoconfigure.WebMvcAutoConfiguration;
@@ -35,6 +36,8 @@ import org.springframework.context.annotation.Import;
 import org.springframework.test.web.reactive.server.WebTestClient;
 import org.springframework.test.web.servlet.MockMvc;
 import org.springframework.test.web.servlet.client.MockMvcWebTestClient;
+import org.springframework.test.web.servlet.client.RestTestClient;
+import org.springframework.web.client.RestClient;
 import org.springframework.web.reactive.function.client.WebClient;
 import org.springframework.web.servlet.DispatcherServlet;
 
@@ -82,4 +85,20 @@ public final class MockMvcAutoConfiguration {
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	@ConditionalOnClass({ RestClient.class, RestTestClient.class })
+	static class RestTestClientMockMvcConfiguration {
+
+		@Bean
+		@ConditionalOnMissingBean
+		RestTestClient restTestClient(MockMvc mockMvc, List<RestTestClientBuilderCustomizer> customizers) {
+			RestTestClient.Builder<?> builder = RestTestClient.bindTo(mockMvc);
+			for (RestTestClientBuilderCustomizer customizer : customizers) {
+				customizer.customize(builder);
+			}
+			return builder.build();
+		}
+
+	}
+
 }

module/spring-boot-webmvc-test/src/test/java/org/springframework/boot/webmvc/test/autoconfigure/MockMvcAutoConfigurationTests.java

@@ -21,6 +21,7 @@ import org.junit.jupiter.api.Test;
 import org.springframework.boot.autoconfigure.AutoConfigurations;
 import org.springframework.boot.test.context.FilteredClassLoader;
 import org.springframework.boot.test.context.runner.WebApplicationContextRunner;
+import org.springframework.boot.web.server.test.client.RestTestClientBuilderCustomizer;
 import org.springframework.boot.web.server.test.client.reactive.WebTestClientBuilderCustomizer;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
@@ -28,6 +29,8 @@ import org.springframework.test.web.reactive.server.WebTestClient;
 import org.springframework.test.web.servlet.MockMvc;
 import org.springframework.test.web.servlet.RequestBuilder;
 import org.springframework.test.web.servlet.assertj.MockMvcTester;
+import org.springframework.test.web.servlet.client.RestTestClient;
+import org.springframework.web.client.RestClient;
 import org.springframework.web.reactive.function.client.WebClient;
 import org.springframework.web.servlet.DispatcherServlet;
 
@@ -41,6 +44,7 @@ import static org.mockito.Mockito.mock;
  *
  * @author Madhura Bhave
  * @author Brian Clozel
+ * @author Stephane Nicoll
  */
 class MockMvcAutoConfigurationTests {
 
@@ -99,6 +103,27 @@ class MockMvcAutoConfigurationTests {
 		});
 	}
 
+	@Test
+	void registersRestTestClient() {
+		this.contextRunner.run((context) -> assertThat(context).hasSingleBean(RestTestClient.class));
+	}
+
+	@Test
+	void shouldNotRegisterRestTestClientIfRestClientIsMissing() {
+		this.contextRunner.withClassLoader(new FilteredClassLoader(RestClient.class))
+			.run((context) -> assertThat(context).doesNotHaveBean(RestTestClient.class));
+	}
+
+	@Test
+	void shouldApplyRestTestClientCustomizers() {
+		this.contextRunner.withUserConfiguration(RestTestClientCustomConfig.class).run((context) -> {
+			assertThat(context).hasSingleBean(RestTestClient.class);
+			assertThat(context).hasBean("myRestTestClientCustomizer");
+			then(context.getBean("myRestTestClientCustomizer", RestTestClientBuilderCustomizer.class)).should()
+				.customize(any(RestTestClient.Builder.class));
+		});
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	static class WebTestClientCustomConfig {
 
@@ -109,4 +134,14 @@ class MockMvcAutoConfigurationTests {
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	static class RestTestClientCustomConfig {
+
+		@Bean
+		RestTestClientBuilderCustomizer myRestTestClientCustomizer() {
+			return mock(RestTestClientBuilderCustomizer.class);
+		}
+
+	}
+
 }

module/spring-boot-webmvc-test/src/test/java/org/springframework/boot/webmvc/test/autoconfigure/mockmvc/MockMvcSpringBootTestIntegrationTests.java

@@ -29,6 +29,7 @@ import org.springframework.context.ApplicationContext;
 import org.springframework.test.context.bean.override.mockito.MockitoBean;
 import org.springframework.test.web.reactive.server.WebTestClient;
 import org.springframework.test.web.servlet.MockMvc;
+import org.springframework.test.web.servlet.client.RestTestClient;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
@@ -84,6 +85,11 @@ class MockMvcSpringBootTestIntegrationTests {
 		webTestClient.get().uri("/one").exchange().expectStatus().isOk().expectBody(String.class).isEqualTo("one");
 	}
 
+	@Test
+	void shouldTestWithRestTestClient(@Autowired RestTestClient restTestClient) {
+		restTestClient.get().uri("/one").exchange().expectStatus().isOk().expectBody(String.class).isEqualTo("one");
+	}
+
 	@Test
 	void shouldNotFailIfFormattingValueThrowsException(CapturedOutput output) throws Exception {
 		this.mvc.perform(get("/formatting")).andExpect(content().string("formatting")).andExpect(status().isOk());

module/spring-boot-webmvc-test/src/test/java/org/springframework/boot/webmvc/test/autoconfigure/mockmvc/MockMvcTesterSpringBootTestIntegrationTests.java

@@ -29,6 +29,7 @@ import org.springframework.context.ApplicationContext;
 import org.springframework.test.context.bean.override.mockito.MockitoBean;
 import org.springframework.test.web.reactive.server.WebTestClient;
 import org.springframework.test.web.servlet.assertj.MockMvcTester;
+import org.springframework.test.web.servlet.client.RestTestClient;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -80,6 +81,11 @@ class MockMvcTesterSpringBootTestIntegrationTests {
 		webTestClient.get().uri("/one").exchange().expectStatus().isOk().expectBody(String.class).isEqualTo("one");
 	}
 
+	@Test
+	void shouldTestWithRestTestClient(@Autowired RestTestClient restTestClient) {
+		restTestClient.get().uri("/one").exchange().expectStatus().isOk().expectBody(String.class).isEqualTo("one");
+	}
+
 	@Test
 	void shouldNotFailIfFormattingValueThrowsException(CapturedOutput output) {
 		assertThat(this.mvc.get().uri("/formatting")).hasStatusOk().hasBodyTextEqualTo("formatting");