When using timeout to simulate "no-message" scenario, other regular test cases stop working about kafka-junit HOT 4 CLOSED

There's not enough information here for me to give you a good answer. Please provide a minimal test case that reproduces the issue.

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Updated the code sample above to include the working test case. When you execute A or B individually, they will pass always. When you run the whole test suite where first A is executed then B, B will always fail.

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OK, so this is interesting. First of all, KafkaHelper#consumeStrings is only good for happy path usage because otherwise the timeout/cancellation of the Future would fail to properly close the consumer. (I kind of regret adding those helpers but now it's too late to change the API.) Because the consumer is running in a background thread and has not been cleanly shutdown, it is interfering with the subsequent tests. This is because you have pinned the Kafka rule to use a fixed port -- which allows the zombie consumer to reconnect to the Kafka broker spun up for the next test in the suite.

So, the hacky way to make your tests pass is to use a random Kafka port for each test by changing the rule creation to look as follows:

@Rule
public KafkaJunitRule kafkaRule = new KafkaJunitRule(EphemeralKafkaBroker.create());

// If you really need to know he Kafka port, it can be found by calling kafkaRule.helper().kafkaPort()

However, the better way (IMO) to write the tests would be as follows:

public class SomeTest {
    private static int kafkaBrokerPort = 9000;

    private final String MY_TOPIC = "my-topic";

    @Rule
    public KafkaJunitRule kafkaRule = new KafkaJunitRule(EphemeralKafkaBroker.create(kafkaBrokerPort)).waitForStartup();

    @Test
    public void A() {
        try (KafkaConsumer<String, String> consumer = kafkaRule.helper().createStringConsumer()) {
            consumer.subscribe(Lists.newArrayList(MY_TOPIC));
            ConsumerRecords<String, String> records = consumer.poll(Duration.ofSeconds(10));
            assertTrue(records.isEmpty());
        } 
    }

    @Test
    public void B() throws InterruptedException, TimeoutException, ExecutionException {
        KafkaHelper helper = kafkaRule.helper();
        helper.produceStrings(MY_TOPIC, "a", "b", "c", "d", "e");
        List<String> result = helper.consumeStrings(MY_TOPIC, 5).get(10, TimeUnit.SECONDS);
        assertEquals(5, result.size());
    }
}

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Hi,
Thanks for the answer. It worked nicely when i created a separate consumer for each broker. Probably it will help to change the example in the README.md file to not show consumeStrings.

What are your thoughts on testing 'no message' scenarios ? I searched a lot but seems like not everyone implements them. Yet i wanted to try because they seem relevant in my case. Those waiting times drastically increase the test cases run time, but i see no other good way to implement that.

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