使用Testconainers来进行JAVA测试

在JAVA项目中，我们需要对代码进行单元测试和集成测试。在测试中，我们需要用到一些外部系统如Kafka，数据库等，常用的做法是Mock这些服务或者搭建测试环境。Mock服务不能完全模拟外部系统，而搭建测试环境的工作量又比较大，另外有些时候测试环境会被多个测试项目共享，互相之间会有干扰。

Testcontainers是一个开源项目，提供了通过加载镜像的服务来提供测试所需要的环境。在官网上我们可以看到现在支持了很多常见的服务，这里我也测试了一下如何用Testcontainers来做单元测试。

假设我们有以下的类，其提供了一个方法，根据输入的消息主题，开始时间戳和结束时间戳，获取Kafka消息的相关分区以及实际的截至时间戳，从而获取指定时间范围内的消息。代码如下：

public class CheckKafkaMsgTimestamp {
    private static final Logger LOG = LoggerFactory.getLogger(CheckKafkaMsgTimestamp.class);
   
    public static KafkaResult getTimestamp(String bootstrapServer, String topic, long startTimestamp, long stopTimestamp) {
        long max_timestamp = stopTimestamp;
        long max_records = 5L;
        Properties props = new Properties();
        props.setProperty("bootstrap.servers", bootstrapServer);
        props.setProperty("group.id", "test");
        props.setProperty("enable.auto.commit", "true");
        props.setProperty("auto.commit.interval.ms", "1000");
        props.setProperty("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
        props.setProperty("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
        KafkaConsumer consumer = new KafkaConsumer<>(props);
 
        // Get all the partitions of the topic
        int partition_num = consumer.partitionsFor(topic).size();
        HashMap search_map = new HashMap<>();
        ArrayList tp = new ArrayList<>();
        for (int i=0;i
            search_map.put(new TopicPartition(topic, i), stopTimestamp);
            tp.add(new TopicPartition(topic, i));
        }
        // Check if message exist with timestamp greater than search timestamp
        Boolean flag = true;
        ArrayList selected_tp = new ArrayList<>();
        Map results = consumer.offsetsForTimes(search_map);
        for (Map.Entry entry : results.entrySet()) {
            OffsetAndTimestamp value = entry.getValue();
            if (value==null) {   //there is at least one partition don't have timestamp greater or equal to the stopTime
                flag = false;
                break;
            }
        }
        // Get the latest timestamp of all partitions if the above check result is false
        // Note the timestamp is the earliest of all the partitions. 
        if (!flag) {
            max_timestamp = 0L;
            consumer.assign(tp);
            Map endoffsets = consumer.endOffsets(tp);
            for (Map.Entry entry : endoffsets.entrySet()) {
                Long temp_timestamp = 0L;
                int record_count = 0;
                TopicPartition t = entry.getKey();
                long offset = entry.getValue();
                if (offset < 1) {
                    LOG.warn("Can not get max_timestamp as partition has no record!");
                    continue;
                }
                consumer.assign(Arrays.asList(t));
                consumer.seek(t, offset>max_records?offset-5:0);
            
                Iterator> records = consumer.poll(Duration.ofSeconds(2)).iterator();
                while (records.hasNext()) {
                    record_count++;
                    ConsumerRecord record = records.next();
                    LOG.info("Topic: {}, Record Timestamp: {}, recordcount: {}", t, record.timestamp(), record_count);
                    if (temp_timestamp == 0L || record.timestamp() > temp_timestamp) {
                        temp_timestamp = record.timestamp();
                    }
                }
                if (temp_timestamp > 0L && temp_timestamp > startTimestamp) {
                    if (max_timestamp == 0L || max_timestamp > temp_timestamp) {
                        max_timestamp = temp_timestamp;
                    }
                    selected_tp.add(t);
                }
            }
        } else {
            selected_tp = tp;
        }
        consumer.close();
        LOG.info("Max Timestamp: {}", max_timestamp);
        return new KafkaResult(max_timestamp, selected_tp);
    }
}

现在我们要对这个功能做单元测试，可以用Testcontainers来起一个Kafka环境。首先我们在pom.xml里面增加以下依赖

<dependency>
  <groupId>org.testcontainersgroupId>
  <artifactId>testcontainersartifactId>
  <version>1.19.1version>
  <scope>testscope>
dependency>
<dependency>
  <groupId>org.testcontainersgroupId>
  <artifactId>kafkaartifactId>
  <version>1.19.1version>
  <scope>testscope>
dependency>
<dependency>
  <groupId>junitgroupId>
  <artifactId>junitartifactId>
  <version>4.13.2version>
dependency>
<dependency>
  <groupId>org.hamcrestgroupId>
  <artifactId>hamcrest-allartifactId>
  <version>1.3version>
  <scope>testscope>
dependency>

然后编写以下的测试代码：

@RunWith(JUnit4.class)
@FixMethodOrder(MethodSorters.NAME_ASCENDING)
public class CheckKafkaMsgTimestampTest {
    private String bootstrapServer;
    private Producer producer;
 
    @Rule
    public KafkaContainer kafka = new KafkaContainer(DockerImageName.parse("confluentinc/cp-kafka:6.2.1"));
 
    @Before
    public void setUp() {
        kafka.start();
        bootstrapServer = kafka.getBootstrapServers();
        // Create a test topic with 3 partitions
        Properties adminProps = new Properties();
        adminProps.put(AdminClientConfig.BOOTSTRAP_SERVERS_CONFIG, bootstrapServer);
        Admin admin = Admin.create(adminProps);
        int partitions = 3;
        short replicationFactor = 1;
        NewTopic newTopic = new NewTopic("test", partitions, replicationFactor);
        CreateTopicsResult result = admin.createTopics(
            Collections.singleton(newTopic)
        );
        try {
            KafkaFuture future = result.values().get("test");
            future.get();
        } catch (Exception e) {
            System.out.println(e.getMessage());
        }
 
        // Create a producer
        Properties props = new Properties();
        props.put("bootstrap.servers", bootstrapServer);
        props.put("acks", "all");
        props.put("retries", 0);
        props.put("linger.ms", 1);
        props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
        props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");
        producer = new KafkaProducer<>(props);
    }
 
    @After
    public void tearDown() {
        producer.close();
        kafka.stop();
    }
 
    @Test
    public void testGetTimestamp() {
        // Prepare 6 messages to send to test topic
        // Each partition will receive 2 message
        long ts = System.currentTimeMillis()-5000L;
        producer.send(new ProducerRecord("test", 0, ts+100, "", "test message"));
        producer.send(new ProducerRecord("test", 0, ts+300, "", "test message"));
        producer.send(new ProducerRecord("test", 1, ts+110, "", "test message"));
        producer.send(new ProducerRecord("test", 1, ts+200, "", "test message"));
        producer.send(new ProducerRecord("test", 2, ts+105, "", "test message"));
        producer.send(new ProducerRecord("test", 2, ts+250, "", "test message"));
 
        KafkaResult result = CheckKafkaMsgTimestamp.getTimestamp(bootstrapServer, "test", ts, System.currentTimeMillis());
        assertEquals(ts+200, result.max_timestamp);
        assertEquals(3, result.selected_tp.size());
 
        result = CheckKafkaMsgTimestamp.getTimestamp(bootstrapServer, "test", ts+500, System.currentTimeMillis());
        assertEquals(0, result.max_timestamp);
        assertEquals(0, result.selected_tp.size());
 
        result = CheckKafkaMsgTimestamp.getTimestamp(bootstrapServer, "test", ts+205, System.currentTimeMillis());
        assertEquals(ts+250, result.max_timestamp);
        assertEquals(2, result.selected_tp.size());
    }
}

解释一下代码，在Rule里面我们用Testcontainer加载了一个Kafka的镜像，然后在Before里面我们启动了Kafka服务，并获取bootstrapserver的地址，然后我们就可以在Kafka里面创建一个包含3个分区的消息主题。

在testGetTimestamp方法中，我们先发送了几条消息到不同的消息分区，然后就可以调用CheckKafkaMsgTimestamp的方法来进行测试和验证了。

如果我们有多个测试要用到同一个Kafka，那么还可以创建一个抽象类，把Kafka的加载定义在这个抽象类中，其他测试类继承这个抽象类。例如

public abstract class AbstractContainerBaseTest {
    public static final KafkaContainer KAFKA_CONTAINER;
 
    static {
        KAFKA_CONTAINER = new KafkaContainer(DockerImageName.parse("confluentinc/cp-kafka:6.2.1"));;
        KAFKA_CONTAINER.start();
    }
}

然后改写一下刚才我们的测试类

public class CheckKafkaMsgTimestampTest extends AbstractContainerBaseTest {
    //@Rule
    //public KafkaContainer kafka = new KafkaContainer(DockerImageName.parse("confluentinc/cp-kafka:6.2.1"));
 
    @Before
    public void setUp() {
        //kafka.start();
        //bootstrapServer = kafka.getBootstrapServers();
        bootstrapServer = KAFKA_CONTAINER.getBootstrapServers();