verifyNoInteractions works with mock but not with spy

Question

Eg.

@Component open class AService {
  @Autowired private lateinit var anotherService: AnotherService

  ...
  ...
  
  fun methodCall() {
   anotherService.methodCall()
  }

}

@Service
open class AnotherService{
  @Autowired private lateinit var aRepo: ARepo

  fun methodCall() {
    aRepo.something()
  }
}

@WebAppConfiguration
@ActiveProfiles("test")
@RunWith(SpringJUnit4ClassRunner::class)
@SpringBootTest(classes = [TestAppConfig::class])
open class MyTest {
 @MockBean private lateinit var aRepo: ARepo
 @SpyBean private lateinit var anotherService: AnotherService
 @Autowired private lateinit var aservice: AService
  
 @Before fun setUp() {
    MockitoAnnotations.openMocks(this)
 }

 @Test
 fun shouldNotInteractWithARepo() {
  
  aservice.methodCall() // Call to Test
  
  verifyNoInteractions(aRepo) // This works and fails as expected
  //verifyNoInteractions(anotherService) // Expect to fail since there is actually a call being made on this spy but it passes.
 }

aRepo does an external network call. I have mocked it at an application level. Similarly anotherService is the encapsulating service in which aRepo makes the network call. I have spied anotherService because I want to verify at times that there is no interaction with it and at times, I want its actual behavior.

In the examples shown, I have only considedred the first case of no interaction. Testing of the actual behavior with @Spy works fine.

verifyNoInteractions on the spied field(anotherService) always passes. Why is this ?. The same when I use it on the Mocked field(aRepo), it works and fails as expected.

How do I setup in a way that if anotherService.methodCall() happens, the test should fail ?