GH-186 ensured FluxReturnValueConfiguration is used

Ensured that regardless of the version of Spring and presense of webflux, the FluxReturnValueConfiguration is used
Resolves #186

spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/HeadersToMessageTests.java

@@ -0,0 +1,73 @@
+/*
+ * Copyright 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.cloud.function.web;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import java.net.URI;
+import java.util.function.Function;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
+import org.springframework.boot.test.web.client.TestRestTemplate;
+import org.springframework.context.annotation.Bean;
+import org.springframework.http.ResponseEntity;
+import org.springframework.messaging.Message;
+import org.springframework.messaging.support.MessageBuilder;
+import org.springframework.test.context.junit4.SpringRunner;
+
+/**
+ *
+ * @author Oleg Zhurakousky
+ *
+ */
+@RunWith(SpringRunner.class)
+@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT, properties = {"spring.cloud.function.web.path=/functions" })
+public class HeadersToMessageTests {
+
+	@Autowired
+	private TestRestTemplate rest;
+
+	@Test
+	public void testBodyAndCustomHeaderFromMessagePropagation() throws Exception {
+		ResponseEntity<String> postForEntity = rest.postForEntity(new URI("/functions/employee"), "{\"name\":\"Bob\",\"age\":25}", String.class);
+		assertEquals("{\"name\":\"Bob\",\"age\":25}", postForEntity.getBody());
+		assertTrue(postForEntity.getHeaders().containsKey("x-content-type"));
+		assertEquals("application/xml", postForEntity.getHeaders().get("x-content-type").get(0));
+		assertEquals("bar", postForEntity.getHeaders().get("foo").get(0));
+	}
+
+	@EnableAutoConfiguration
+	@org.springframework.boot.test.context.TestConfiguration
+	protected static class TestConfiguration {
+		@Bean({ "employee"})
+	    public Function<Message<String>, Message<String>> function() {
+			return request -> {
+				Message<String> message = MessageBuilder.withPayload(request.getPayload())
+						.setHeader("X-Content-Type", "application/xml")
+						.setHeader("foo", "bar")
+						.build();
+				return message;
+			};
+	    }
+	}
+}
+