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：
java
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<String, String> consumer = new KafkaConsumer<>(props);
// Get all the partitions of the topic
int partition_num = consumer.partitionsFor(topic).size();
HashMap<TopicPartition, Long> search_map = new HashMap<>();
ArrayList<TopicPartition> tp = new ArrayList<>();
for (int i=0;i<partition_num;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<TopicPartition> selected_tp = new ArrayList<>();
Map<TopicPartition, OffsetAndTimestamp> results = consumer.offsetsForTimes(search_map);
for (Map.Entry<TopicPartition, OffsetAndTimestamp> 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<TopicPartition, Long> endoffsets = consumer.endOffsets(tp);
for (Map.Entry<TopicPartition, Long> 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<ConsumerRecord<String, String>> records = consumer.poll(Duration.ofSeconds(2)).iterator();
while (records.hasNext()) {
record_count++;
ConsumerRecord<String, String> 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
XML
<dependency>
<groupId>org.testcontainers</groupId>
<artifactId>testcontainers</artifactId>
<version>1.19.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.testcontainers</groupId>
<artifactId>kafka</artifactId>
<version>1.19.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.13.2</version>
</dependency>
<dependency>
<groupId>org.hamcrest</groupId>
<artifactId>hamcrest-all</artifactId>
<version>1.3</version>
<scope>test</scope>
</dependency>然后编写以下的测试代码：
java
@RunWith(JUnit4.class)
@FixMethodOrder(MethodSorters.NAME_ASCENDING)
public class CheckKafkaMsgTimestampTest {
private String bootstrapServer;
private Producer<String, String> 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<Void> 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<String, String>("test", 0, ts+100, "", "test message"));
producer.send(new ProducerRecord<String, String>("test", 0, ts+300, "", "test message"));
producer.send(new ProducerRecord<String, String>("test", 1, ts+110, "", "test message"));
producer.send(new ProducerRecord<String, String>("test", 1, ts+200, "", "test message"));
producer.send(new ProducerRecord<String, String>("test", 2, ts+105, "", "test message"));
producer.send(new ProducerRecord<String, String>("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
java
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
java
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();