Unable to unit test a @KafkaListener annotated method

问题

I'm trying to unit test a kafka consumer class, in Spring. I want to know that if a kafka message is sent to it's topic, the listener method was called correctly. My consumer class is annotated like this:

@KafkaListener(topics = "${kafka.topics.myTopic}")
public void myKafkaMessageEvent(final String message) { ...

If I @Autowire a consumer, when I send a kafka message, the listener method is called correctly, but I can't assert that the method was called because the class isn't a mock.

If I mock a consumer, when I send a kafka message the listener method is not called at all. I can call the method directly, and assert that it worked, but that doesn't do what I want, which is to check if the method is called when I send a kafka message to it's topic.

For now I have resorted to put a counter inside the consumer, and increment it every time the listener method is called, then check that it's value has been changed. Making a variable just for testing seems like a terrible solution to me.

Is there maybe a way to make the mocked consumer receive the kafka messages too? Or some other way to assert that the non-mocked consumer listener method was called?

回答1:

Sounds like you are requesting something similar what we have in Spring AMQP Testing Framework: https://docs.spring.io/spring-amqp/docs/2.0.3.RELEASE/reference/html/_reference.html#test-harness

So, if you are not good with extra variable you can borrow that solution and implement your own "harness".

I think that should be a good addition to the Framework so, please, raise an appropriate issue and we can together bring such a tool for the public.

UPDATE

So, according Spring AMQP foundation I did this in my test configuration:

public static class KafkaListenerTestHarness extends KafkaListenerAnnotationBeanPostProcessor {

    private final Map<String, Object> listeners = new HashMap<>();

    @Override
    protected void processListener(MethodKafkaListenerEndpoint endpoint, KafkaListener kafkaListener,
            Object bean, Object adminTarget, String beanName) {

        bean = Mockito.spy(bean);

        this.listeners.put(kafkaListener.id(), bean);

        super.processListener(endpoint, kafkaListener, bean, adminTarget, beanName);
    }

    @SuppressWarnings("unchecked")
    public <T> T getSpy(String id) {
        return (T) this.listeners.get(id);
    }

}

...

@SuppressWarnings("rawtypes")
@Bean(name = KafkaListenerConfigUtils.KAFKA_LISTENER_ANNOTATION_PROCESSOR_BEAN_NAME)
@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
public static KafkaListenerTestHarness kafkaListenerAnnotationBeanPostProcessor() {
    return new KafkaListenerTestHarness();
}

Then in the target test-case I use it like this:

@Autowired
private KafkaListenerTestHarness harness;
...
Listener listener = this.harness.getSpy("foo");

verify(listener, times(2)).listen1("foo");

来源：https://stackoverflow.com/questions/50214261/unable-to-unit-test-a-kafkalistener-annotated-method

标签

Spring

unit-testing

apache-kafka

spring-kafka