DemoApplicationTests.java

// in testing module

package com.example.demo;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.kafka.core.KafkaTemplate;
import org.springframework.kafka.test.EmbeddedKafkaBroker;
import org.springframework.kafka.test.context.EmbeddedKafka;
import org.springframework.kafka.test.rule.EmbeddedKafkaRule;
import org.springframework.test.context.junit4.SpringRunner;

import static org.hamcrest.CoreMatchers.equalTo;
import static org.hamcrest.MatcherAssert.assertThat;

@RunWith(SpringRunner.class)
@SpringBootTest
@EmbeddedKafka(partitions = 1, brokerProperties = {"listeners=PLAINTEXT://localhost:9092", "port=9092"})
public class DemoApplicationTests {

	@Autowired
	private Consumer consumer;

	@Autowired
	private KafkaTemplate<String, String> kafkaTemplate;
	private String myTestingTopic = "myTestingTopic";

	@Test
	public void contextLoads() throws InterruptedException {
		kafkaTemplate.send(myTestingTopic, "Hello");
		Thread.sleep(10000);
		assertThat(consumer.getList().size(), equalTo(1));
		System.out.printf("Hello received");
		System.out.println(consumer.getList());
	}


	public EmbeddedKafkaBroker getEmbeddedKafka() {
		String[] topics = new String[1];
		topics[0] = myTestingTopic;
		EmbeddedKafkaRule embeddedKafkaRule= new EmbeddedKafkaRule(1,  false, topics);
		return embeddedKafkaRule.getEmbeddedKafka();
	}
}

/* output:
received payload=ConsumerRecord(topic = myTestingTopic, partition = 0, offset = 0, CreateTime = 1556559649127, serialized key size = -1, serialized value size = 5, headers = RecordHeaders(headers = [], isReadOnly = false), key = null, value = Hello)
Hello received[ConsumerRecord(topic = myTestingTopic, partition = 0, offset = 0, CreateTime = 1556559649127, serialized key size = -1, serialized value size = 5, headers = RecordHeaders(headers = [], isReadOnly = false), key = null, value = Hello)]
*/

// in main package

package com.example.demo;

import lombok.Data;
import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.springframework.kafka.annotation.KafkaListener;
import org.springframework.stereotype.Component;

import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;

@Component
@Data
public class Consumer {

    List<String> list= new CopyOnWriteArrayList<>();

    @KafkaListener(topics = "${kafkatest.topic}")
    public void receive(ConsumerRecord<?, ?> consumerRecord) {
        System.out.println("received payload="+consumerRecord.toString());
        list.add(consumerRecord.toString());
    }
}


// pom.xml file

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.1.4.RELEASE</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.example</groupId>
	<artifactId>demo</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>demo</name>
	<description>Demo project for Spring Boot</description>

	<properties>
		<java.version>1.8</java.version>
		<junit.jupiter.version>5.3.2</junit.jupiter.version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
		<dependency>
			<groupId>org.apache.kafka</groupId>
			<artifactId>kafka-streams</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.kafka</groupId>
			<artifactId>spring-kafka</artifactId>
		</dependency>

		<dependency>
			<groupId>org.projectlombok</groupId>
			<artifactId>lombok</artifactId>
			<optional>true</optional>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>
		<dependency>
			<groupId>org.springframework.kafka</groupId>
			<artifactId>spring-kafka-test</artifactId>
			<scope>test</scope>
		</dependency>
		<dependency>
			<groupId>org.springframework.kafka</groupId>
			<artifactId>spring-kafka-test</artifactId>
		</dependency>
		<dependency>
			<groupId>org.junit.vintage</groupId>
			<artifactId>junit-vintage-engine</artifactId>
			<version>${junit.jupiter.version}</version>
			<scope>test</scope>
		</dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>

</project>


// properties file
spring.kafka.consumer.auto-offset-reset=earliest
spring.kafka.consumer.group-id=myTestGroupId
kafkatest.topic=myTestingTopic