Mock SenderResult in ReactiveKafkaProducerTemplate send method - apache-kafka

Question

I am trying to mock the send method for reactiveKafkaConsumerTemplate.
#Mock
private ReactiveKafkaConsumerTemplate<String, String> reactiveKafkaConsumerTemplate;
#Mock
private ReactiveKafkaProducerTemplate<String, List<Object>> reactiveKafkaProducerTemplate;
Mockito.when(reactiveKafkaConsumerTemplate.receiveAutoAck())
.thenReturn(createConsumerRecords(2));
Mockito.when(reactiveKafkaProducerTemplate
.send(Mockito.anyString(),Mockito.anyString(),Mockito.anyList()))
.thenReturn(???);
I am trying to mock the send method of reactiveProducerTemplate to return a SenderResult. Is it possible to do so? If yes, can someone point me to documentation/sample to do this. I have spend a lot time looking for solution but couldn't find any.
Update: I tried the following as per suggestions from Gary
ProducerRecord<String, List<Object>> record
= new ProducerRecord<String, List<Object>>(topic,"key", objectSetup.setup());
RecordMetadata meta
= new RecordMetadata(new TopicPartition("topic",0),0,0,0,(long)1,2,1);
Mockito.when(reactiveKafkaProducerTemplate.send(topic,"key",objectSetup.setup())
.thenReturn(Mono.just(new SendResult<>(record, meta))));
I get the following exception at line .thenReturn(Mono.just(new SendResult<>(record, meta)))). It doesn't mention what is null in the exception and I don't see anything that is null.
java.lang.NullPointerException
at com.ServiceTests.cTestMethod(ServiceTests.java:69)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:688)
at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:131)
at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:149)
at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestableMethod(TimeoutExtension.java:140)
at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestMethod(TimeoutExtension.java:84)
at org.junit.jupiter.engine.execution.ExecutableInvoker$ReflectiveInterceptorCall.lambda$ofVoidMethod$0(ExecutableInvoker.java:115)
at org.junit.jupiter.engine.execution.ExecutableInvoker.lambda$invoke$0(ExecutableInvoker.java:105)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain$InterceptedInvocation.proceed(InvocationInterceptorChain.java:106)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain.proceed(InvocationInterceptorChain.java:64)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain.chainAndInvoke(InvocationInterceptorChain.java:45)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain.invoke(InvocationInterceptorChain.java:37)
at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:104)
at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:98)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeTestMethod$6(TestMethodTestDescriptor.java:210)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:206)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:131)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:65)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
Update 2: I am able to create the mock with the code snippet from Gary. Here is the code that I am trying to test
public void sendToKafka(ConsumerRecord<String, String> consumerRecord){
log.info("sending to topic={}, {}={},", destinationTopic, Metric.class.getSimpleName(), consumerRecord);
List<Object> metrics = transformRecord(consumerRecord);
kafkaProducerTemplate.send(destinationTopic, consumerRecord.key(), metrics)
.doOnSuccess(senderResult -> log.info("sent {} offset : {}", metrics, senderResult.recordMetadata().offset()))
.doOnError(throwable -> log.error("Error while sending message to destination topic : {}", throwable.getMessage()))
.subscribe();
}
When I call this method from my test, I can see that the template is the mock template however, I get a java.lang.NullPointerException on the line
.doOnSuccess(senderResult -> log.info("sent {} offset : {}", metrics, senderResult.recordMetadata().offset()))
The exception doesn't give any details on what is null. I confirmed consumerRecord and metrics is not null.
Found the issue was with the setup. The actual code is expecting 3 parameters and in the set up I had mocked only with 2 parameters for send method.
Updated the code to:
when(reactiveKafkaProducerTemplate.send(Mockito.anyString(),Mockito.anyString(), Mockito.anyList())).thenReturn(Mono.just(result));

Answer 1

#Test
void test() {
ReactiveKafkaProducerTemplate<String, String> template = mock(ReactiveKafkaProducerTemplate.class);
RecordMetadata meta = new RecordMetadata(new TopicPartition("foo", 0), 0L, 0L, 0L, 0L, 0, 2);
SenderResult result = mock(SenderResult.class);
when(result.recordMetadata()).thenReturn(meta);
when(template.send("foo", "bar")).thenReturn(Mono.just(result));
template.send("foo", "bar")
.doOnNext(sr -> {
assertThat(sr.recordMetadata().toString()).isEqualTo("foo-0#0");
})
.subscribe();
}