Can't stub SimpleMessageListenerContainer isActive method [Spring AMQP Rabbit] - spring-boot

Question

I'm trying to create unit tests for my Spring EventListeners that toggle SimpleMessageListenerContainer (start/stop).
The code I'm trying to test:
#Configuration
public class SpringEventsListeners {
private static CPLocation cpLocation = CPLoggingFactory.createCPLocation(SpringEventsListeners.class);
private ConfigurationServiceImpl configService;
//Constructor Injection for Testability.
public SpringEventsListeners(final ConfigurationServiceImpl configService) {
this.configService = configService;
}
/**
* Rabbit listeners might be started/stopped after a refresh depending on a property.
* In case a change is needed, we perform it.
*/
#EventListener(classes= { ApplicationReadyEvent.class, EnvironmentChangeEvent.class })
public void handleRabbitListenerToggle() {
String method = "handleRabbitListenerToggle";
cpLocation.info(method, "Received refresh event. Determining action.");
boolean shouldActivateRabbit = configService.shouldActivateRabbitListeners();
for (SimpleMessageListenerContainer container : configService.getAllRabbitSimpleMessageListenerContainers()) {
if (shouldActivateRabbit && !container.isActive()) {
container.start();
cpLocation.info(method, "Starting container: "+Arrays.toString(container.getQueueNames()));
}
else if (!shouldActivateRabbit && container.isActive()) {
container.shutdown();
cpLocation.info(method, "Shutting down container: "+Arrays.toString(container.getQueueNames()));
}
}
}
}
Minimal test (tests nothing):
#RunWith(MockitoJUnitRunner.class)
public class SpringEventsListenersTests {
#InjectMocks
private SpringEventsListeners classUnderTest;
#Mock
private ConfigurationServiceImpl mockConfigurationService;
#Mock
private SimpleMessageListenerContainer mockSimpleMessageListenerContainer;
#Test
public void testToggleTrue() {
//Given
given(mockConfigurationService.shouldActivateRabbitListeners()).willReturn(true);
given(mockConfigurationService.getAllRabbitSimpleMessageListenerContainers()).willReturn(Arrays.asList(mockSimpleMessageListenerContainer));
given(mockSimpleMessageListenerContainer.isActive()).willReturn(false);
//When
classUnderTest.handleRabbitListenerToggle();
Assert.assertThat(true, is(true));
}
}
The tests won't run as I receive a NullPointerException on given(mockSimpleMessageListenerContainer.isActive()).willReturn(false);:
java.lang.NullPointerException at
org.springframework.amqp.rabbit.listener.AbstractMessageListenerContainer.isActive(AbstractMessageListenerContainer.java:1271)
at
com.cp.order.listener.SpringEventsListenersTests.testToggleTrue(SpringEventsListenersTests.java:36)
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.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at
org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at
org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at
org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325) at
org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at
org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290) at
org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71) at
org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288) at
org.junit.runners.ParentRunner.access$000(ParentRunner.java:58) at
org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268) at
org.junit.runners.ParentRunner.run(ParentRunner.java:363) at
org.mockito.internal.runners.DefaultInternalRunner$1.run(DefaultInternalRunner.java:79)
at
org.mockito.internal.runners.DefaultInternalRunner.run(DefaultInternalRunner.java:85)
at
org.mockito.internal.runners.StrictRunner.run(StrictRunner.java:39)
at
org.mockito.junit.MockitoJUnitRunner.run(MockitoJUnitRunner.java:163)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137) at
com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at
com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
at
com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
at
com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
I will also need to assert that .shutdown or .start were called on the container, so it needs to be mocked.

Answer 1

Mockito can't mock final methods (isActive() is final).
You could use reflection (e.g. DirectFieldAccessor) to check the active field instead.
That said, mocking the listener container is rather unusual; it is a complex piece of code; perhaps you could explain exactly what you are trying to test?