How to create a test for DeadLetter Kafka

Question

In my little microservice, I created a Producer Kafka to send the messages with errors (messages having errors in the JSON format) inside the DeadLetter in this way :

@Component
public class KafkaProducer {
    @Autowired
    private KafkaTemplate<String, String> kafkaTemplate;
    public void sendDeadLetter(String message) {
        kafkaTemplate.send("DeadLetter", message);
    }
}

I would like to create a JUnitTest for the completeness of the project, but I have no idea how to create the eventuality of a possible JSON error in order to create the test. I thank everyone for any possible help and advice

Hi michalk, could you show me an example structure for the simple "send" test in this case? If you could kindly answer my question so that I can then accept the answer to you — Jacket, Feb 28 '21 at 17:25
https://github.com/ConsenSysMesh/kafka-deadletter/tree/master/src/test — aran, Mar 02 '21 at 12:56
Hi aran,I saw your link but I was unable to adapt the tests to my deadLetter above, also due to my inexperience, could you help me in structuring a test to see the correct reception of the message? If you could answer me as an answer and not a comment I can mark you as the correct answer — Jacket, Mar 03 '21 at 08:42
@aran I just need a test on the correct reception of the message — Jacket, Mar 03 '21 at 08:43

score 3 · Accepted Answer · edited Mar 09 '21 at 18:58

To create a JUnitTest consistent with your code. I should recreate the case where you pass it a warped or invalid JSON. In your case, I would opt to configure a MockConsumer from which to read any message that the logic of your code will be invited to the dead letter. To have a usable test structure, I recommend something like this:

@KafkaListener(topics = "yourTopic")
public void listen(String message) {
messages.add(message);
}

For testing a basic structure could be

@Test
 public void testDeadLetter(){

//Set up a mockConsumer
MockConsumer<String,String> yourMockConsumer = new MockConsumer<String,String>   (OffsetResetStrategy.EARLIEST);
yourMockConsumer.subscribe(Collections.singletonList("yourTopic"));

//Sending message on embedded Kafka broker
String error = "ERRORE";
kafkaTemplate.send("yourTopic", error);
//Reading the message may take a second
Thread.sleep(1000);
//Create an Assert that checks you that the message is equal to the error specified           above
 }

I hope it will be useful to you!

score 2 · Answer 2 · answered Mar 08 '21 at 18:01

2

You can create Kafka topic using testcontainers and write your tests on top of that.

Sharing an example on how to use testcontainers https://github.com/0001vrn/testcontainers-example

answered Mar 08 '21 at 18:01

Varun Thakur

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How to create a test for DeadLetter Kafka

2 Answers2