Support @SpringBootTest with @ContextHierarchy

Update SpringBootTestContextBootstrapper to detect `@ContextHierarchy`
annotations so that only the last child creates a
`WebApplicationContext`.

Prior to this commit a context hierarchy would start two embedded web
servers which is inconsistent with the `SpringApplicationBuilder`
behavior.

Fixes gh-8311

spring-boot-test/src/test/java/org/springframework/boot/test/context/SpringBootTestWebEnvironmentContextHierarchyTests.java

@@ -0,0 +1,75 @@
+/*
+ * Copyright 2012-2017 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.boot.test.context;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.AbstractSpringBootTestEmbeddedWebEnvironmentTests.AbstractConfig;
+import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
+import org.springframework.boot.test.context.SpringBootTestWebEnvironmentContextHierarchyTests.ChildConfiguration;
+import org.springframework.boot.test.context.SpringBootTestWebEnvironmentContextHierarchyTests.ParentConfiguration;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.ContextHierarchy;
+import org.springframework.test.context.junit4.SpringRunner;
+import org.springframework.web.bind.annotation.RestController;
+import org.springframework.web.context.WebApplicationContext;
+import org.springframework.web.servlet.config.annotation.EnableWebMvc;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link SpringBootTest} configured with {@link WebEnvironment#DEFINED_PORT}.
+ *
+ * @author Phillip Webb
+ * @author Andy Wilkinson
+ */
+@RunWith(SpringRunner.class)
+@DirtiesContext
+@SpringBootTest(webEnvironment = WebEnvironment.DEFINED_PORT, properties = {
+		"server.port=0", "value=123" })
+@ContextHierarchy({ @ContextConfiguration(classes = ParentConfiguration.class),
+		@ContextConfiguration(classes = ChildConfiguration.class) })
+public class SpringBootTestWebEnvironmentContextHierarchyTests {
+
+	@Autowired
+	private ApplicationContext context;
+
+	@Test
+	public void testShouldOnlyStartSingleServer() throws Exception {
+		ApplicationContext parent = this.context.getParent();
+		assertThat(this.context).isInstanceOf(WebApplicationContext.class);
+		assertThat(parent).isNotInstanceOf(WebApplicationContext.class);
+	}
+
+	@Configuration
+	protected static class ParentConfiguration extends AbstractConfig {
+
+	}
+
+	@Configuration
+	@EnableWebMvc
+	@RestController
+	protected static class ChildConfiguration extends AbstractConfig {
+
+	}
+
+}