Enable MessageSourceAutoConfiguration when using @WebMvcTest

Closes gh-6608

spring-boot-test-autoconfigure/src/main/resources/META-INF/spring.factories

@@ -59,6 +59,7 @@ org.springframework.boot.autoconfigure.groovy.template.GroovyTemplateAutoConfigu
 org.springframework.boot.autoconfigure.gson.GsonAutoConfiguration,\
 org.springframework.boot.autoconfigure.hateoas.HypermediaAutoConfiguration,\
 org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration,\
+org.springframework.boot.autoconfigure.MessageSourceAutoConfiguration,\
 org.springframework.boot.autoconfigure.mustache.MustacheAutoConfiguration,\
 org.springframework.boot.autoconfigure.thymeleaf.ThymeleafAutoConfiguration,\
 org.springframework.boot.autoconfigure.web.HttpMessageConvertersAutoConfiguration,\

spring-boot-test-autoconfigure/src/test/java/org/springframework/boot/test/autoconfigure/web/servlet/WebMvcTestMessageSourceIntegrationTests.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2012-2016 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.autoconfigure.web.servlet;
+
+import java.util.Locale;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.MessageSource;
+import org.springframework.test.context.TestPropertySource;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Integration tests for {@link WebMvcTest} and {@link MessageSource} auto-configuration.
+ *
+ * @author Andy Wilkinson
+ */
+@RunWith(SpringRunner.class)
+@WebMvcTest(secure = false)
+@TestPropertySource(properties = "spring.messages.basename=web-mvc-test-messages")
+public class WebMvcTestMessageSourceIntegrationTests {
+
+	@Autowired
+	private ApplicationContext context;
+
+	@Test
+	public void messageSourceHasBeenAutoConfigured() {
+		assertThat(this.context.getMessage("a", null, Locale.ENGLISH)).isEqualTo("alpha");
+	}
+
+}

spring-boot-test-autoconfigure/src/test/resources/web-mvc-test-messages.properties

@@ -0,0 +1 @@
+a: alpha