Support detection and with test initializers

Relax `SpringBootTestContextBootstrapper` rules so that a test can
specify an `ApplicationContextInitializer` and still have
`@SpringBootConfiguration` detected.

Prior to this commit detection would not occur because it's possible
that an initializer _could_ register configuration. This scenario is
actually quite unlikely to occur, certainly less likely than wanting to
use an initializer in combination with auto-detection.

Fixes gh-8483

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/validation/DelegatingValidator.java

@@ -71,6 +71,10 @@ public class DelegatingValidator implements SmartValidator {
 		}
 	}
 
+	/**
+	 * Return the delegate validator.
+	 * @return the delegate validator
+	 */
 	protected final Validator getDelegate() {
 		return this.delegate;
 	}

spring-boot-test/src/main/java/org/springframework/boot/test/context/SpringBootTestContextBootstrapper.java

@@ -194,8 +194,7 @@ public class SpringBootTestContextBootstrapper extends DefaultTestContextBootstr
 	protected Class<?>[] getOrFindConfigurationClasses(
 			MergedContextConfiguration mergedConfig) {
 		Class<?>[] classes = mergedConfig.getClasses();
-		if (containsNonTestComponent(classes) || mergedConfig.hasLocations()
-				|| !mergedConfig.getContextInitializerClasses().isEmpty()) {
+		if (containsNonTestComponent(classes) || mergedConfig.hasLocations()) {
 			return classes;
 		}
 		Class<?> found = new SpringBootConfigurationFinder()

spring-boot-test/src/test/java/org/springframework/boot/test/context/bootstrap/SpringBootTestContextBootstrapperWithInitializersTests.java

@@ -0,0 +1,66 @@
+/*
+ * 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.context.bootstrap;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTestContextBootstrapper;
+import org.springframework.boot.test.context.bootstrap.SpringBootTestContextBootstrapperWithInitializersTests.CustomInitializer;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.ApplicationContextInitializer;
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.test.context.BootstrapWith;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Integration tests for {@link SpringBootTestContextBootstrapper} with and
+ * {@link ApplicationContextInitializer}.
+ *
+ * @author Phillip Webb
+ */
+@RunWith(SpringRunner.class)
+@BootstrapWith(SpringBootTestContextBootstrapper.class)
+@ContextConfiguration(initializers = CustomInitializer.class)
+public class SpringBootTestContextBootstrapperWithInitializersTests {
+
+	@Autowired
+	private ApplicationContext context;
+
+	@Test
+	public void foundConfiguration() throws Exception {
+		Object bean = this.context
+				.getBean(SpringBootTestContextBootstrapperExampleConfig.class);
+		assertThat(bean).isNotNull();
+	}
+
+	// gh-8483
+
+	public static class CustomInitializer
+			implements ApplicationContextInitializer<ConfigurableApplicationContext> {
+
+		@Override
+		public void initialize(ConfigurableApplicationContext applicationContext) {
+		}
+
+	}
+
+}