Integration testing and spring application events

I have a spring rest controller which fires a ApplicationEvent

@RestController
public class VehicleController {

@Autowired
private VehicleService service;

@Autowired
private ApplicationEventPublisher eventPublisher;

@RequestMapping(value = "/public/rest/vehicle/add", method = RequestMethod.POST)
public void addVehicle(@RequestBody @Valid Vehicle vehicle){
    service.add(vehicle);
    eventPublisher.publishEvent(new VehicleAddedEvent(vehicle));
    }
}

And I have a integration test for the controller, something like

    @RunWith(SpringRunner.class)
    @WebMvcTest(controllers = VehicleController.class,includeFilters = @ComponentScan.Filter(classes = EnableWebSecurity.class))
    @Import(WebSecurityConfig.class)

public class VehicleControllerTest {
@Autowired
private MockMvc mockMvc;

@MockBean
private VehicleService vehicleService;

@Test
public void addVehicle() throws Exception {
    Vehicle vehicle=new Vehicle();
    vehicle.setMake("ABC");
    ObjectMapper mapper=new ObjectMapper();
    String s = mapper.writeValueAsString(vehicle);

    given(vehicleService.add(vehicle)).willReturn(1);

    mockMvc.perform(post("/public/rest/vehicle/add").contentType(
            MediaType.APPLICATION_JSON).content(s))
            .andExpect(status().isOk());
   }
}

Now, if I remove the event publishing line, the test successes. However, with the event, it hits error.

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.IllegalArgumentException: null source

I tried bunch of different things, to avoid or skip the line in testing but nothing helped. Could you please tell me what is the right way to test such code? Thanks in advance