JUnit-testing a Spring @Async void service method

Question

I have a Spring service:

@Service @Transactional public class SomeService {      @Async     public void asyncMethod(Foo foo) {         // processing takes significant time     } } 

And I have an integration test for this SomeService:

@RunWith(SpringJUnit4ClassRunner.class) @SpringApplicationConfiguration(classes = Application.class) @WebAppConfiguration @IntegrationTest @Transactional public class SomeServiceIntTest {      @Inject     private SomeService someService;          @Test         public void testAsyncMethod() {              Foo testData = prepareTestData();              someService.asyncMethod(testData);              verifyResults();         }          // verifyResult() with assertions, etc. } 

Here is the problem:

• as SomeService.asyncMethod(..) is annotated with @Async and
• as the SpringJUnit4ClassRunner adheres to the @Async semantics

the testAsyncMethod thread will fork the call someService.asyncMethod(testData) into its own worker thread, then directly continue executing verifyResults(), possibly before the previous worker thread has finished its work.

How can I wait for someService.asyncMethod(testData)'s completion before verifying the results? Notice that the solutions to How do I write a unit test to verify async behavior using Spring 4 and annotations? don't apply here, as someService.asyncMethod(testData) returns void, not a Future<?>.

Answer 1

For @Async semantics to be adhered, some active @Configuration class will have the @EnableAsync annotation, e.g.

@Configuration @EnableAsync @EnableScheduling public class AsyncConfiguration implements AsyncConfigurer {    //  } 

To resolve my issue, I introduced a new Spring profile non-async.

If the non-async profile is not active, the AsyncConfiguration is used:

@Configuration @EnableAsync @EnableScheduling @Profile("!non-async") public class AsyncConfiguration implements AsyncConfigurer {    // this configuration will be active as long as profile "non-async" is not (!) active  } 

If the non-async profile is active, the NonAsyncConfiguration is used:

@Configuration // notice the missing @EnableAsync annotation @EnableScheduling @Profile("non-async") public class NonAsyncConfiguration {    // this configuration will be active as long as profile "non-async" is active  } 

Now in the problematic JUnit test class, I explicitly activate the "non-async" profile in order to mutually exclude the async behavior:

@RunWith(SpringJUnit4ClassRunner.class) @SpringApplicationConfiguration(classes = Application.class) @WebAppConfiguration @IntegrationTest @Transactional @ActiveProfiles(profiles = "non-async") public class SomeServiceIntTest {      @Inject     private SomeService someService;          @Test         public void testAsyncMethod() {              Foo testData = prepareTestData();              someService.asyncMethod(testData);              verifyResults();         }          // verifyResult() with assertions, etc. } 

Answer 2

If you are using Mockito (directly or via Spring testing support @MockBean), it has a verification mode with a timeout exactly for this case: https://static.javadoc.io/org.mockito/mockito-core/2.10.0/org/mockito/Mockito.html#22

someAsyncCall(); verify(mock, timeout(100)).someMethod(); 

Much more capable is the great library Awaitility, which has many options how to handle async assertions. Example:

someAsyncCall(); await().atMost(5, SECONDS)   .untilAsserted(() -> assertThat(userRepo.size()).isEqualTo(1));