Sprint Cloud - Kafka Streams Binder - Testing KafkaStreamsProcessor - spring-kafka

Question

I've been trying to write unit tests for a KafkaStreamsProcessor. This is the code processor code
#EnableBinding(KafkaStreamsProcessor.class)
public class StockProcessor {
private static final Log LOG = LogFactory.getLog(StockProcessor.class);
#Autowired
private EddieClient client;
#Autowired
private InventoryRepository inventoryRepository;
#Autowired
private PermissionRepository permissionRepository;
/**
* Receive message from input queue
* Apply business logic
* Send to output queue
*
* #param inputMessage the message
* #return outputMessage
*/
#StreamListener(Processor.INPUT)
#SendTo(Processor.OUTPUT)
public KStream<?, OutputMessage> process(KStream<?, InputMessage> inputMessage){
return inputMessage
.map((key, value) -> {
LOG.info("::: processing message...");
// ... business logic
return new KeyValue<>(key, outputMessage);
});
}
}
aplication.yml
spring:
cloud:
stream:
kafka:
streams:
binder:
brokers:
- ${NX_KAFKA_SERVERS}
bindings:
input:
destination: ${NX_INPUT_TOPIC}
content-type: application/json
group: ${NX_PULL_GROUP_ID}
output:
destination: ${NX_OUTPUT_TOPIC}
content-type: application/json
group: ${NX_PUSH_GROUP_ID}
This is what I've read and tried to do in unit test
public class StockProcessorTest {
private static final String INPUT_TOPIC = "input-topic";
private static final String OUTPUT_TOPIC = "output-topic";
#SpyBean
private StockProcessor stockProcessor;
#MockBean
private EddieClient client;
#MockBean
private InventoryRepository inventoryRepository;
#MockBean
private PermissionRepository permissionRepository;
private TopologyTestDriver topologyTestDriver;
private TestInputTopic<String, InputMessage> inputTopic;
private TestOutputTopic<String, OutputMessage> outputTopic;
private Topology topology;
private Properties config;
KStream<String, InputMessage> inputMessageStream;
KStream<String, OutputMessage> outputMessageStream;
#Before
public void setup() {
config = new Properties();
config.setProperty(StreamsConfig.APPLICATION_ID_CONFIG, "app_id");
config.setProperty(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "foo:1234");
StreamsBuilder streamsBuilder = new StreamsBuilder();
inputMessageStream = streamsBuilder.stream(INPUT_TOPIC);
stockProcessor.process(inputMessageStream).to(OUTPUT_TOPIC);
topology = streamsBuilder.build();
topologyTestDriver = new TopologyTestDriver(topology, config);
//???
}
}
I don't really know if I'am going to right path here. I am using Jackson serializer. How can I create the inputTopic and outputTopic and test my business logic?
I can provide any further detail needed.
Thanks in advance

Answer 1

Here are some examples for how to unit test a Kafka Streams application based on Spring Cloud Stream - https://github.com/spring-cloud/spring-cloud-stream-samples/blob/master/kafka-streams-samples/kafka-streams-word-count/src/test/java/kafka/streams/word/count/WordCountProcessorApplicationTests.java
Also, here is a test suite that has some advanced examples: https://github.com/spring-cloud/spring-cloud-stream-samples/tree/master/kafka-streams-samples/kafka-streams-inventory-count/src/test/java/kafka/streams/inventory/count
These examples have details about how to use Serdes with the test driver.
Please check them out and see if they satisfy your testing requirements.