Testcontainers¶

Testcontainers is a Java library that supports JUnit tests, providing lightweight, throwaway instances that can run in Docker.

The product quickstart documentation explains the basic practices. Below are some practices for the components I am often using.

Test container with Kafka¶

The Kafka test container uses Confluent image.

The following code includes a StrimziKafka test container maas kafka backend. The approach is to use a BasicIT test class that uses the Strimzi container. As the exposed port is mapped to a port dynamically allocated by docker, we can get the bootstrap address and expose it via system variable:

public abstract class BasicIT {

    @ClassRule
    public static StrimziContainer kafkaContainerForTest = new StrimziContainer()
            .withNetwork(network)
            .withNetworkAliases("kafka")
            .withExposedPorts(9092);

    @BeforeAll
    public static void startAll() {
        kafkaContainerForTest.start();
        System.setProperty("KAFKA_BOOTSTRAP_SERVERS", kafkaContainer.getBootstrapServers());
    }

    @AfterAll
    public static void stopAll() {
        kafkaContainerForTest.stop();

    }
}

Then each test extends this class and can access the bootstrap URL

 clusterInfo.adminURL = kafkaContainerForTest.getBootstrapServers();

Or in the case of quarkus test, we need to specify in the application.properties what to get while using the test profile

%test.kafka.bootstrap.servers=${KAFKA_BOOTSTRAP_SERVERS}

Which means a test at the API level will work fine (extracted from the store simulator project):

    @Test
    public void shouldStartSendingOneMessageToKafka(){
        System.out.println(System.getProperty("KAFKA_BOOTSTRAP_SERVERS"));
        given().when().post("/start/kafka/1").then().statusCode(200);
    }