Support for @ControllerAdvice in WebFlux

Issue: SPR-15132

spring-test/src/main/java/org/springframework/test/web/reactive/server/DefaultControllerSpec.java

@@ -15,6 +15,7 @@
  */
 package org.springframework.test.web.reactive.server;
 
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 import java.util.Optional;
@@ -44,6 +45,8 @@ class DefaultControllerSpec implements WebTestClient.ControllerSpec {
 
 	private final List<Object> controllers;
 
+	private final List<Object> controllerAdvice = new ArrayList<>(8);
+
 	private final TestWebFluxConfigurer configurer = new TestWebFluxConfigurer();
 
 
@@ -53,6 +56,12 @@ class DefaultControllerSpec implements WebTestClient.ControllerSpec {
 	}
 
 
+	@Override
+	public DefaultControllerSpec controllerAdvice(Object... controllerAdvice) {
+		this.controllerAdvice.addAll(Arrays.asList(controllerAdvice));
+		return this;
+	}
+
 	@Override
 	public DefaultControllerSpec contentTypeResolver(Consumer<RequestedContentTypeResolverBuilder> consumer) {
 		this.configurer.contentTypeResolverConsumer = consumer;
@@ -103,12 +112,17 @@ class DefaultControllerSpec implements WebTestClient.ControllerSpec {
 
 	@Override
 	public WebTestClient.Builder configureClient() {
+		return WebTestClient.bindToApplicationContext(createApplicationContext());
+	}
+
+	protected AnnotationConfigApplicationContext createApplicationContext() {
 		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
 		this.controllers.forEach(controller -> registerBean(context, controller));
+		this.controllerAdvice.forEach(advice -> registerBean(context, advice));
 		context.register(DelegatingWebFluxConfiguration.class);
 		context.registerBean(WebFluxConfigurer.class, () -> this.configurer);
 		context.refresh();
-		return WebTestClient.bindToApplicationContext(context);
+		return context;
 	}
 
 	@SuppressWarnings("unchecked")

spring-test/src/main/java/org/springframework/test/web/reactive/server/WebTestClient.java

@@ -179,6 +179,13 @@ public interface WebTestClient {
 	 */
 	interface ControllerSpec {
 
+		/**
+		 * Register one or more
+		 * {@link org.springframework.web.bind.annotation.ControllerAdvice
+		 * ControllerAdvice} instances to be used in tests.
+		 */
+		ControllerSpec controllerAdvice(Object... controllerAdvice);
+
 		/**
 		 * Customize content type resolution.
 		 * @see WebFluxConfigurer#configureContentTypeResolver