Add bindToHttpHandler to WebTestClient

Issue: SPR-15499

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

@@ -77,13 +77,13 @@ class DefaultWebTestClient implements WebTestClient {
 
 
 	DefaultWebTestClient(WebClient.Builder webClientBuilder, ClientHttpConnector connector,
-			ExchangeMutatingWebFilter exchangeMutatingWebFilter, Duration timeout) {
+			ExchangeMutatingWebFilter filter, Duration timeout) {
 
 		Assert.notNull(webClientBuilder, "WebClient.Builder is required");
 
 		this.wiretapConnector = new WiretapConnector(connector);
 		this.webClient = webClientBuilder.clientConnector(this.wiretapConnector).build();
-		this.exchangeMutatingWebFilter = exchangeMutatingWebFilter;
+		this.exchangeMutatingWebFilter = (filter != null ? filter : new ExchangeMutatingWebFilter());
 		this.timeout = (timeout != null ? timeout : Duration.ofSeconds(5));
 	}
 

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

@@ -35,6 +35,7 @@ import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
 import org.springframework.http.client.reactive.ClientHttpRequest;
 import org.springframework.http.codec.ServerCodecConfigurer;
+import org.springframework.http.server.reactive.HttpHandler;
 import org.springframework.util.MultiValueMap;
 import org.springframework.validation.Validator;
 import org.springframework.web.reactive.accept.RequestedContentTypeResolverBuilder;
@@ -140,7 +141,7 @@ public interface WebTestClient {
 	// Static, factory methods
 
 	/**
-	 * Integration testing without a server, targeting specific annotated,
+	 * Integration testing without a server targeting specific annotated,
 	 * WebFlux controllers. The default configuration is the same as for
 	 * {@link org.springframework.web.reactive.config.EnableWebFlux @EnableWebFlux}
 	 * but can also be further customized through the returned spec.
@@ -152,7 +153,7 @@ public interface WebTestClient {
 	}
 
 	/**
-	 * Integration testing without a server, with WebFlux infrastructure detected
+	 * Integration testing without a server with WebFlux infrastructure detected
 	 * from an {@link ApplicationContext} such as {@code @EnableWebFlux}
 	 * Java config and annotated controller Spring beans.
 	 * @param applicationContext the context
@@ -164,7 +165,7 @@ public interface WebTestClient {
 	}
 
 	/**
-	 * Integration testing without a server, targeting WebFlux functional endpoints.
+	 * Integration testing without a server targeting WebFlux functional endpoints.
 	 * @param routerFunction the RouterFunction to test
 	 * @return the {@link WebTestClient} builder
 	 */
@@ -172,6 +173,15 @@ public interface WebTestClient {
 		return new RouterFunctionSpec(routerFunction);
 	}
 
+	/**
+	 * Integration testing without a server targeting the given HttpHandler.
+	 * @param httpHandler the handler to test
+	 * @return the {@link WebTestClient} builder
+	 */
+	static Builder bindToHttpHandler(HttpHandler httpHandler) {
+		return new DefaultWebTestClientBuilder(httpHandler, null);
+	}
+
 	/**
 	 * Complete end-to-end integration tests with actual requests to a running server.
 	 * @return the {@link WebTestClient} builder

spring-test/src/test/java/org/springframework/test/web/reactive/server/samples/bind/HttpHandlerTests.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2002-2017 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.test.web.reactive.server.samples.bind;
+
+import java.nio.charset.StandardCharsets;
+import java.util.Collections;
+
+import org.junit.Test;
+import reactor.core.publisher.Mono;
+
+import org.springframework.core.io.buffer.DataBuffer;
+import org.springframework.core.io.buffer.DefaultDataBufferFactory;
+import org.springframework.http.server.reactive.HttpHandler;
+import org.springframework.test.web.reactive.server.WebTestClient;
+import org.springframework.web.server.WebFilter;
+import org.springframework.web.server.adapter.WebHttpHandlerBuilder;
+
+/**
+ * Bind to an {@link HttpHandler}.
+ * @author Rossen Stoyanchev
+ */
+public class HttpHandlerTests {
+
+
+	@Test
+	public void testWebFilter() throws Exception {
+
+		WebFilter myFilter = (exchange, chain) -> {
+			DataBuffer buffer = new DefaultDataBufferFactory().allocateBuffer();
+			buffer.write("It works!".getBytes(StandardCharsets.UTF_8));
+			return exchange.getResponse().writeWith(Mono.just(buffer));
+		};
+
+		HttpHandler httpHandler = WebHttpHandlerBuilder.webHandler(exchange -> Mono.empty())
+				.filters(Collections.singletonList(myFilter)).build();
+
+		WebTestClient.bindToHttpHandler(httpHandler).build()
+				.get().uri("/")
+				.exchange()
+				.expectStatus().isOk()
+				.expectBody(String.class).isEqualTo("It works!");
+	}
+
+}