Serialisation issue with spring-boot controller testing

I have my controller test set up like this:

@ExtendWith(SpringExtension.class)
@WebAppConfiguration()
@ContextConfiguration(classes = {MyController.class, MyExceptionHandler.class})
@EnableWebMvc
public class TeilzahlungControllerTest {
    @Autowired
    private MockMvc mockMvc;
    //test the controller
}

I refactored it from a bulky test, that ran on @SpringBootTest. So now my new test runs about 100 times faster, but it no longer has "all the beans". And it shows on deserialization: certain objects are no longer deserialized correctly, with the biggest example being Instant.

You may also see that I had to "manually" include my "global" Exceptionhandler (MyExceptionHandler.class).

So my question is: how can I make sure that my slim ApplicationContext contains all the beans required, especially those for deserialization? Including them by hand can not be the solution, right?

Many thanks in advance!