Is it better to write integration or unit test for Kafka Spring?

I’ve been searching a while about the best way to test Kafka in Spring. As far as I know, @EmbeddedKafka is more for an unit test but isn’t it better to test Kafka in a real working environment by writing integration test for it? And what really am I testing by writing unit test for Kafka? A real working producer and consumer should be more meaningful than mocking the kafka. What do you suggest?

Answer

EmbeddedKafka is an integration test. It starts a real broker, not a mock, for you to interact with.

For unit testing, Kafka provides its own mocks for consumer and producer, not reliant on Spring libraries

what really am I testing by writing unit test for Kafka

Your general processing logic, including error handling and deserialization

In Kafka Streams, you can also control the timing of the records for testing aggregation logic based on simulated windows