Sample Test Case with Embedded Kafka

pom.xml

<?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>

	<groupId>com.example</groupId>
	<artifactId>kafka-test-sample</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>kafka-test-sample</name>
	<description>Demo project for Spring Boot</description>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.0.5.RELEASE</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
		<java.version>1.8</java.version>
	</properties>

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

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


</project>

SimpleKafkaTest.java

package com.example.kafkatestsample;


import org.apache.kafka.clients.consumer.Consumer;
import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.clients.producer.Producer;
import org.apache.kafka.clients.producer.ProducerRecord;
import org.apache.kafka.common.serialization.StringDeserializer;
import org.apache.kafka.common.serialization.StringSerializer;
import org.junit.After;
import org.junit.Before;
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.DefaultKafkaConsumerFactory;
import org.springframework.kafka.core.DefaultKafkaProducerFactory;
import org.springframework.kafka.test.context.EmbeddedKafka;
import org.springframework.kafka.test.rule.KafkaEmbedded;
import org.springframework.kafka.test.utils.KafkaTestUtils;
import org.springframework.test.context.junit4.SpringRunner;

import java.util.HashMap;
import java.util.Map;

import static java.util.Collections.singleton;
import static org.assertj.core.api.Assertions.assertThat;

@RunWith(SpringRunner.class)
@SpringBootTest
@EmbeddedKafka
public class SimpleKafkaTest {

    private static final String TOPIC = "domain-events";

    @Autowired
    private KafkaEmbedded kafkaEmbedded;

    private Consumer<String, String> consumer;


    @Before
    public void setUp() {
        Map<String, Object> configs = new HashMap<>(KafkaTestUtils.consumerProps("consumer", "false", kafkaEmbedded));
        consumer = new DefaultKafkaConsumerFactory<>(configs, new StringDeserializer(), new StringDeserializer()).createConsumer();
        consumer.subscribe(singleton(TOPIC));
        consumer.poll(0);
    }

    @After
    public void tearDown() {
        consumer.close();
    }

    @Test
    public void kafkaSetup_withTopic_ensureSendMessageIsReceived() {
        // Arrange
        Map<String, Object> configs = new HashMap<>(KafkaTestUtils.producerProps(kafkaEmbedded));
        Producer<String, String> producer = new DefaultKafkaProducerFactory<>(configs, new StringSerializer(), new StringSerializer()).createProducer();

        // Act
        producer.send(new ProducerRecord<>(TOPIC, "my-aggregate-id", "{\"event\":\"Test Event\"}"));
        producer.flush();

        // Assert
        ConsumerRecord<String, String> singleRecord = KafkaTestUtils.getSingleRecord(consumer, TOPIC);
        assertThat(singleRecord).isNotNull();
        assertThat(singleRecord.key()).isEqualTo("my-aggregate-id");
        assertThat(singleRecord.value()).isEqualTo("{\"event\":\"Test Event\"}");
    }

}