How to test an aspect with SpringBootTest?

I had similar problem. My Aspect is listening on controller methods. To get it activated, importing the AnnotationAwareAspectJAutoProxyCreator made the trick:

@RunWith(SpringRunner.class)
@Import(AnnotationAwareAspectJAutoProxyCreator.class) // activate aspect
@WebMvcTest(MyController.class)
public class MyControllerTest {

    ...

}

You have to put @EnableAspectJAutoProxy with your file @Configuration that declares the bean with @Aspect.

@Aspect
@Configuration
@EnableAspectJAutoProxy
public class TimeLoggerAspect {

  private static final Logger log = LoggerFactory.getLogger(TimeLoggerAspect.class);

  @Around("@annotation(demo.TimeLogger)")
  public Object methodTimeLogger(ProceedingJoinPoint joinPoint) 
          throws Throwable {
    long startTime = System.currentTimeMillis();

    Object proceed = joinPoint.proceed();

    long totalTime = System.currentTimeMillis() - startTime;
    log.info("Method " + joinPoint.getSignature() + ": " + totalTime + "ms");

    return proceed;
  }
}

I think that will do the work.

You need to start an @SpringBootApplication. However, it does not have to be the one you use to start your app in production. It can be a special one for this test only and can be in your test sources root not your src.

@SpringBootApplication
@ComponentScan(basePackageClasses = {DemoComponent.class, TimeLoggerAspect.class})
public class SpringBootTestMain {
    public static void main(String[] args) {
        SpringApplication.run(SpringBootTestMain.class, args);
    }

}

Then in your test this is the only class you need to list.

@ExtendWith(SpringExtension.class)
@SpringBootTest(classes = SpringBootTestMain.class)
public class DemoComponentFailTest {

Another solution that seems to work is adding AnnotationAwareAspectJAutoProxyCreator in classes of @SpringBootTest, although I am not quite certain why.

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit.jupiter.SpringExtension;

@ExtendWith(SpringExtension.class)
@SpringBootTest(classes = { DemoComponent.class, 
                            TimeLoggerAspect.class,
                            AnnotationAwareAspectJAutoProxyCreator.class })
public class DemoComponentFailTest {

  @Autowired
  private DemoComponent demoComponent;

  @Test
  public void shouldLogMethodTiming() {
      demoComponent.sayHello();
  }
}