Add support for using WebFlux's WebTestClient to document an API

Closes gh-384

docs/src/test/java/com/example/webtestclient/PerTestPreprocessing.java

@@ -0,0 +1,42 @@
+/*
+ * Copyright 2014-2017 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 com.example.webtestclient;
+
+import org.springframework.test.web.reactive.server.WebTestClient;
+
+import static org.springframework.restdocs.operation.preprocess.Preprocessors.preprocessRequest;
+import static org.springframework.restdocs.operation.preprocess.Preprocessors.preprocessResponse;
+import static org.springframework.restdocs.operation.preprocess.Preprocessors.prettyPrint;
+import static org.springframework.restdocs.operation.preprocess.Preprocessors.removeHeaders;
+import static org.springframework.restdocs.webtestclient.WebTestClientRestDocumentation.document;
+
+public class PerTestPreprocessing {
+
+	// @formatter:off
+
+	private WebTestClient webTestClient;
+
+	public void general() {
+		// tag::preprocessing[]
+		this.webTestClient.get().uri("/").exchange().expectStatus().isOk().expectBody()
+			.consumeWith(document("index",
+				preprocessRequest(removeHeaders("Foo")), // <1>
+				preprocessResponse(prettyPrint()))); // <2>
+		// end::preprocessing[]
+	}
+
+}