Allow custom WebTestClient beans

Update `@SpringBootTest` `WebTestClient` support so that the bean
definition is only registered when the user has not defined or
auto-configured their own.

See gh-10556

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/web/reactive/server/NoWebTestClientBeanChecker.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.reactive.server;
+
+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.ListableBeanFactory;
+import org.springframework.context.annotation.ImportSelector;
+import org.springframework.core.type.AnnotationMetadata;
+import org.springframework.test.web.reactive.server.WebTestClient;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * {@link ImportSelector} to check no {@link WebTestClient} definition is registered when
+ * config classes are processed.
+ */
+class NoWebTestClientBeanChecker implements ImportSelector, BeanFactoryAware {
+
+	@Override
+	public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
+		assertThat(BeanFactoryUtils.beanNamesForTypeIncludingAncestors(
+				(ListableBeanFactory) beanFactory, WebTestClient.class)).isEmpty();
+	}
+
+	@Override
+	public String[] selectImports(AnnotationMetadata importingClassMetadata) {
+		return new String[0];
+	}
+
+}

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/web/reactive/server/WebTestClientContextCustomizerIntegrationTests.java

@@ -0,0 +1,81 @@
+/*
+ * 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.reactive.server;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import reactor.core.publisher.Mono;
+
+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.boot.web.embedded.tomcat.TomcatReactiveWebServerFactory;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Import;
+import org.springframework.core.io.buffer.DefaultDataBufferFactory;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.server.reactive.HttpHandler;
+import org.springframework.http.server.reactive.ServerHttpRequest;
+import org.springframework.http.server.reactive.ServerHttpResponse;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.context.junit4.SpringRunner;
+import org.springframework.test.web.reactive.server.WebTestClient;
+
+/**
+ * Integration test for {@link WebTestClientContextCustomizer}.
+ *
+ * @author Phillip Webb
+ */
+@RunWith(SpringRunner.class)
+@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT, properties = "spring.main.web-application-type=reactive")
+@DirtiesContext
+public class WebTestClientContextCustomizerIntegrationTests {
+
+	@Autowired
+	private WebTestClient webTestClient;
+
+	@Test
+	public void test() {
+		this.webTestClient.get().uri("/").exchange().expectBody(String.class)
+				.isEqualTo("hello");
+	}
+
+	@Configuration
+	@Import({ TestHandler.class, NoWebTestClientBeanChecker.class })
+	static class TestConfig {
+
+		@Bean
+		public TomcatReactiveWebServerFactory webServerFactory() {
+			return new TomcatReactiveWebServerFactory(0);
+		}
+
+	}
+
+	static class TestHandler implements HttpHandler {
+
+		private static final DefaultDataBufferFactory factory = new DefaultDataBufferFactory();
+
+		@Override
+		public Mono<Void> handle(ServerHttpRequest request, ServerHttpResponse response) {
+			response.setStatusCode(HttpStatus.OK);
+			return response.writeWith(Mono.just(factory.wrap("hello".getBytes())));
+		}
+
+	}
+
+}

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/web/reactive/server/WebTestClientContextCustomizerWithOverrideIntegrationTests.java

@@ -0,0 +1,93 @@
+/*
+ * 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.reactive.server;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import reactor.core.publisher.Mono;
+
+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.boot.web.embedded.tomcat.TomcatReactiveWebServerFactory;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Import;
+import org.springframework.core.io.buffer.DefaultDataBufferFactory;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.server.reactive.HttpHandler;
+import org.springframework.http.server.reactive.ServerHttpRequest;
+import org.springframework.http.server.reactive.ServerHttpResponse;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.context.junit4.SpringRunner;
+import org.springframework.test.web.reactive.server.WebTestClient;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.mock;
+
+/**
+ * Integration test for {@link WebTestClientContextCustomizer} with a custom
+ * {@link WebTestClient} bean.
+ *
+ * @author Phillip Webb
+ */
+@RunWith(SpringRunner.class)
+@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT, properties = "spring.main.web-application-type=reactive")
+@DirtiesContext
+public class WebTestClientContextCustomizerWithOverrideIntegrationTests {
+
+	@Autowired
+	private WebTestClient webTestClient;
+
+	@Test
+	public void test() {
+		assertThat(this.webTestClient).isInstanceOf(CustomWebTestClient.class);
+	}
+
+	@Configuration
+	@Import({ TestHandler.class, NoWebTestClientBeanChecker.class })
+	static class TestConfig {
+
+		@Bean
+		public TomcatReactiveWebServerFactory webServerFactory() {
+			return new TomcatReactiveWebServerFactory(0);
+		}
+
+		@Bean
+		public WebTestClient webTestClient() {
+			return mock(CustomWebTestClient.class);
+		}
+
+	}
+
+	static class TestHandler implements HttpHandler {
+
+		private static final DefaultDataBufferFactory factory = new DefaultDataBufferFactory();
+
+		@Override
+		public Mono<Void> handle(ServerHttpRequest request, ServerHttpResponse response) {
+			response.setStatusCode(HttpStatus.OK);
+			return response.writeWith(Mono.just(factory.wrap("hello".getBytes())));
+		}
+
+	}
+
+	interface CustomWebTestClient extends WebTestClient {
+
+	}
+
+}