Poprawki

src/main/java/edu/my/example/kafka/Sender.java

@@ -14,7 +14,11 @@ public class Sender {
     private KafkaTemplate<String,String> kafkaTemplate;
 
     public void send(String topic, String payload){
-        log.info("sending payload='{}' to topic ='{}'",payload,topic);
-        kafkaTemplate.send(topic,payload);
+        int i=10;
+        while(i>0) {
+            log.info("sending payload='{}' to topic ='{}'", payload, topic);
+            kafkaTemplate.send(topic, payload);
+            i--;
+        }
     }
 }

src/test/java/edu/my/example/kafka/SpringKafkaApplicationTest.java

@@ -4,7 +4,6 @@ import static org.assertj.core.api.Assertions.assertThat;
 
 import java.util.concurrent.TimeUnit;
 
-import kafka.server.KafkaServer;
 import org.junit.ClassRule;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -12,7 +11,6 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.test.context.SpringBootTest;
-import org.springframework.kafka.test.context.EmbeddedKafka;
 import org.springframework.kafka.test.rule.KafkaEmbedded;
 import org.springframework.test.annotation.DirtiesContext;
 import org.springframework.test.context.junit4.SpringRunner;
@@ -21,6 +19,7 @@ import org.springframework.test.context.junit4.SpringRunner;
 @SpringBootTest
 @DirtiesContext
 public class SpringKafkaApplicationTest {
+
   private static final Logger log = LoggerFactory.getLogger(SpringKafkaApplicationTest.class);
   private static String BOOT_TOPIC = "boot.t";
 
@@ -31,8 +30,8 @@ public class SpringKafkaApplicationTest {
   private Consumer receiver;
 
   @ClassRule
-  public static KafkaEmbedded embeddedKafka =
-          new KafkaEmbedded(1, true, BOOT_TOPIC);
+  public static KafkaEmbedded embeddedKafka = new KafkaEmbedded(1, true, BOOT_TOPIC);
+
   @Test
   public void testReceive() throws Exception {
     sender.send(BOOT_TOPIC, "Hello Boot!");