Can I test kafka-streams suppress logic? - apache-kafka

Question

My application use kafka streams suppress logic.
I want to test kafka streams topology using suppress.
Runnning uinit test, My topology not emit result.
Kafka streams logic
...
.suppress(Suppressed.untilTimeLimit(Duration.ofSeconds(5), Suppressed.BufferConfig.maxBytes(1_000_000_000L).emitEarlyWhenFull()))
...
My test case code.
After create input data, running test case cant't read suppress logic output record.
just return null
testDriver.pipeInput(recordFactory.create("input", key, dummy, 0L));
System.out.println(testDriver.readOutput("streams-result", Serdes.String().deserializer(), serde.deserializer()));
Can i test my suppress logic?

Answer 1

The simple answer is yes.
Some good references are Confluent Example Tests this example in particular tests the suppression feature. And many other examples always a good place to check first. Here is another example of mine written in Kotlin.
An explanation of the feature and testing it can be found in post 3 on this blog post
Some key points:
The window will only emit the final result as expected from the documents.
To flush the final results you will need to send an extra dummy event as seen in the examples such as confluents here.
You will need to manipulate the event time to test it as suppression works off the event time this can be provided by the test input topic API or use a custom TimestampExtractor.
For testing I recommend setting the following to remove cache and reduce commit interval.
props[StreamsConfig.CACHE_MAX_BYTES_BUFFERING_CONFIG] = 0
props[StreamsConfig.COMMIT_INTERVAL_MS_CONFIG] = 5
Hope this helps.