Polish @IntegrationComponentScan auto-configuration

See gh-2037
See gh-7718

spring-boot-samples/spring-boot-sample-integration/src/test/java/sample/integration/consumer/SampleIntegrationApplicationTests.java

@@ -23,9 +23,8 @@ import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
 import java.util.concurrent.TimeUnit;
 
-import org.junit.AfterClass;
+import org.junit.After;
 import org.junit.Before;
-import org.junit.BeforeClass;
 import org.junit.Test;
 import sample.integration.SampleIntegrationApplication;
 import sample.integration.producer.ProducerApplication;
@@ -48,32 +47,37 @@ import static org.assertj.core.api.Assertions.assertThat;
  */
 public class SampleIntegrationApplicationTests {
 
-	private static ConfigurableApplicationContext context;
-
-	@BeforeClass
-	public static void start() throws Exception {
-		context = SpringApplication.run(SampleIntegrationApplication.class);
-	}
-
-	@AfterClass
-	public static void stop() {
-		if (context != null) {
-			context.close();
-		}
-	}
+	private ConfigurableApplicationContext context;
 
 	@Before
 	public void deleteOutput() {
+		FileSystemUtils.deleteRecursively(new File("target/input"));
 		FileSystemUtils.deleteRecursively(new File("target/output"));
 	}
 
+	@After
+	public void stop() {
+		if (this.context != null) {
+			this.context.close();
+		}
+	}
+
 	@Test
 	public void testVanillaExchange() throws Exception {
+		this.context = SpringApplication.run(SampleIntegrationApplication.class);
 		SpringApplication.run(ProducerApplication.class, "World");
 		String output = getOutput();
 		assertThat(output).contains("Hello World");
 	}
 
+	@Test
+	public void testMessageGateway() throws Exception {
+		this.context = SpringApplication.run(SampleIntegrationApplication.class,
+				"testviamg");
+		String output = getOutput();
+		assertThat(output).contains("testviamg");
+	}
+
 	private String getOutput() throws Exception {
 		Future<String> future = Executors.newSingleThreadExecutor()
 				.submit(new Callable<String>() {