No bean found for definition [SpyDefinition... when using #SpyBean - spring

Question

I have an application that listens for Kafka messages using #KafkaListener inside of a #Component. Now I'd like to make an integration test with a Kafka test container (which spins up Kafka in the background). In my test I want to verify that the listener method was called and finished, however when I use #SpyBean in my test I get:
No bean found for definition [SpyDefinition#7a939c9e name = '', typeToSpy = com.demo.kafka.MessageListener, reset = AFTER]
I'm using Kotling, important classes:
Class to test
#Component
class MessageListener(private val someRepository: SomeRepository){
#KafkaListener
fun listen(records: List<ConsumerRecord<String, String>>) {
// do something with someRepository
}
}
Base test class
#ExtendWith(SpringExtension::class)
#SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.MOCK)
#TestInstance(TestInstance.Lifecycle.PER_CLASS)
class KafkaContainerTests {
// some functionality to spin up kafka testcontainer
}
Test class
class MessageListenerTest #Autowired constructor(
private val someRepository: SomeRepository
) : KafkaContainerTests() {
#SpyBean
private lateinit var messageListenerSpy: MessageListener
private var messageListenerLatch = CountDownLatch(1)
#BeforeAll
fun setupLatch() {
logger.debug("setting up latch")
doAnswer {
it.callRealMethod()
messageListenerLatch.count
}.whenever(messageListenerSpy).listen(any())
}
#Test
fun testListener(){
sendKafkaMessage(someValidKafkaMessage)
// assert that the listen method is being called & finished
assertTrue(messageListenerLatch.await(20, TimeUnit.SECONDS))
// and assert someRepository is called
}
}
The reason I am confused is that when I add the MessageListener to the #Autowired constructor of the MessageListenerTest it does get injected successfully.
Why is the test unable to find the bean when using #SpyBean?

Answer 1

It works fine for me with Java:
#SpringBootTest
class So58184716ApplicationTests {
#SpyBean
private Listener listener;
#Test
void test(#Autowired KafkaTemplate<String, String> template) throws InterruptedException {
template.send("so58184716", "foo");
CountDownLatch latch = new CountDownLatch(1);
willAnswer(inv -> {
inv.callRealMethod();
latch.countDown();
return null;
}).given(this.listener).listen("foo");
assertThat(latch.await(10, TimeUnit.SECONDS)).isTrue();
verify(this.listener).listen("foo");
}
}
#SpringBootApplication
public class So58184716Application {
public static void main(String[] args) {
SpringApplication.run(So58184716Application.class, args);
}
#Bean
public NewTopic topic() {
return TopicBuilder.name("so58184716").partitions(1).replicas(1).build();
}
}
#Component
class Listener {
#KafkaListener(id = "so58184716", topics = "so58184716")
public void listen(String in) {
System.out.println(in);
}
}