Improve reliability of kafka sample integration test

spring-boot-samples/spring-boot-sample-kafka/src/test/java/sample/kafka/SampleKafkaApplicationTests.java

@@ -16,10 +16,9 @@
 package sample.kafka;
 
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.extension.RegisterExtension;
 
+import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.test.context.SpringBootTest;
-import org.springframework.boot.test.extension.OutputCapture;
 import org.springframework.kafka.test.context.EmbeddedKafka;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -36,17 +35,18 @@ import static org.assertj.core.api.Assertions.assertThat;
 @EmbeddedKafka(topics = "testTopic")
 class SampleKafkaApplicationTests {
 
-	@RegisterExtension
-	OutputCapture output = new OutputCapture();
+	@Autowired
+	private Consumer consumer;
 
 	@Test
 	void testVanillaExchange() throws Exception {
-		long end = System.currentTimeMillis() + 30000;
-		while (!this.output.toString().contains("A simple test message")
+		long end = System.currentTimeMillis() + 10000;
+		while (this.consumer.getMessages().isEmpty()
 				&& System.currentTimeMillis() < end) {
 			Thread.sleep(250);
 		}
-		assertThat(this.output).contains("A simple test message");
+		assertThat(this.consumer.getMessages()).extracting("message")
+				.containsOnly("A simple test message");
 	}
 
 }