JUnit tests for AspectJ

Question

I am trying to write Junit tests for Custom Aspect. Here is the Aspect Class Snippet:

@Aspect @Component public class SampleAspect {      private static Logger log = LoggerFactory.getLogger(SampleAspect.class);      @Around("execution(* org.springframework.data.mongodb.core.MongoOperations.*(..)) || execution(* org.springframework.web.client.RestOperations.*(..))")     public Object intercept(final ProceedingJoinPoint point) throws Throwable {         logger.info("invoked Cutom aspect");          return point.proceed();      }  } 

So the above aspect intercepts whenever jointpoint matches the pointcut. Its working fine.

But my question is how to unit test that class. I have the following Junit Test:

@Test(expected = MongoTimeoutException.class)     public void TestWithMongoTemplate() {         //MongoDocument class         TestDocument test = new TestDocument();          ApplicationContext ctx = new AnnotationConfigApplicationContext(TestMongoConfigurationMain.class);         MongoTemplate mongoTemplate = ctx.getBean(MongoTemplate.class);          //this call is being intercepted by SampleAspect         mongoTemplate.save(test);      } 

So my mongoTemplate.save(test) in Junit is being intercepted by SampleAspect as it matches pointcut. But how should I make sure in junits(probably by asserting) that my SampleAspect is intercepting when that joint point is invoked?

I cannot assert on return value from intercept() as it does nothing special other than executing joint point. So my Junit cannot find any difference whether its being executed by aspect or a regular execution based on return values.

Any code snippets examples on aspect testing would be great if provided.Thanks

Answer 1

I think what you are trying to test is aspect weaving and pointcut matching. Please note that that would be an integration rather than a unit test. If you really want to unit test your aspect logic and because you have tagged the question by "mockito" anyway, I suggest you do just that: Write a unit test and mock the aspect's joinpoint and maybe its other parameters, if any. Here is a slightly more complex example with some intra-aspect logic:

Java class to be targeted by aspect:

package de.scrum_master.app;  public class Application {     public static void main(String[] args) {         new Application().doSomething(11);         new Application().doSomething(-22);         new Application().doSomething(333);     }      public void doSomething(int number) {         System.out.println("Doing something with number " + number);     } } 

Aspect under test:

package de.scrum_master.aspect;  import org.aspectj.lang.ProceedingJoinPoint; import org.aspectj.lang.annotation.Around; import org.aspectj.lang.annotation.Aspect;  @Aspect public class SampleAspect {     @Around("execution(* doSomething(int)) && args(number)")     public Object intercept(final ProceedingJoinPoint thisJoinPoint, int number) throws Throwable {         System.out.println(thisJoinPoint + " -> " + number);         if (number < 0)             return thisJoinPoint.proceed(new Object[] { -number });         if (number > 99)             throw new RuntimeException("oops");         return thisJoinPoint.proceed();     } } 

Console log when running Application.main(..):

As you can see, the aspect passes on 11, negates -22 and throws an exception for 333:

execution(void de.scrum_master.app.Application.doSomething(int)) -> 11 Doing something with number 11 execution(void de.scrum_master.app.Application.doSomething(int)) -> -22 Doing something with number 22 execution(void de.scrum_master.app.Application.doSomething(int)) -> 333 Exception in thread "main" java.lang.RuntimeException: oops     at de.scrum_master.aspect.SampleAspect.intercept(SampleAspect.aj:15)     at de.scrum_master.app.Application.doSomething(Application.java:10)     at de.scrum_master.app.Application.main(Application.java:7) 

Unit test for aspect:

Now we really want to verify that the aspect does what it should and cover all execution paths:

package de.scrum_master.aspect;  import org.aspectj.lang.ProceedingJoinPoint; import org.junit.Rule; import org.junit.Test; import org.mockito.Mock; import org.mockito.junit.MockitoJUnit; import org.mockito.junit.MockitoRule;  import static org.mockito.Mockito.*;  public class SampleAspectTest {     @Rule     public MockitoRule mockitoRule = MockitoJUnit.rule();      @Mock     private ProceedingJoinPoint proceedingJoinPoint;      private SampleAspect sampleAspect = new SampleAspect();      @Test     public void testPositiveSmallNumber() throws Throwable {         sampleAspect.intercept(proceedingJoinPoint, 11);         // 'proceed()' is called exactly once         verify(proceedingJoinPoint, times(1)).proceed();         // 'proceed(Object[])' is never called         verify(proceedingJoinPoint, never()).proceed(null);     }      @Test     public void testNegativeNumber() throws Throwable {         sampleAspect.intercept(proceedingJoinPoint, -22);         // 'proceed()' is never called         verify(proceedingJoinPoint, never()).proceed();         // 'proceed(Object[])' is called exactly once         verify(proceedingJoinPoint, times(1)).proceed(new Object[] { 22 });     }      @Test(expected = RuntimeException.class)     public void testPositiveLargeNumber() throws Throwable {         sampleAspect.intercept(proceedingJoinPoint, 333);     } } 

Now run this simple JUnit + Mockito test in order to test the aspect logic in isolation, not the wiring/weaving logic. For the latter you would need another type of test.

P.S.: Only for you I used JUnit and Mockito. Usually I just use Spock and its built-in mocking capabilities. ;-)