I have a method in service file –>

public FeedbackResponseDTO createFeedback(@Valid @NonNull FeedbackRequestDTO feedbackRequestDTO, @Valid @NonNull String channelName) {

        // in v2: channelName is already set in feedbackRequestDTO
        log.info("Class: {}, Method: {}, Object: {}", this.getClass().getName(), "createFeedback", "checking ssfqId");
        ServicesStageFeedbackQuestionMappings servicesStageMappingsEntity = servicesStageQuestionMappingsService
                .getMappingsById(feedbackRequestDTO.getServicesStageFeedbackQuestionMappingsId());

        Feedback feedbackInput = convertFKeysToEntity (feedbackRequestDTO, servicesStageMappingsEntity);

        log.info("Class: {}, Method: {}, Object: {}", this.getClass().getName(), "createFeedback", "saving feedback");
        Feedback feedbackSaved = feedbackRepo.save(feedbackInput);
        log.info("Class: {}, Method: {}, Object: {}", this.getClass().getName(), "createFeedback", "saved feedback with id "+ feedbackSaved.getId());
        return FeedbackResponseDTO.builder().id(feedbackSaved.getId()).build();
    }

The coverage in intellij is 100% but mutation is failing with line
replaced return value with null for service/impl/FeedbackServiceV2::createFeedback → SURVIVED

I wrote a test case but didnt worked –>

@Test
    void testCreateFeedback_WhenFeedbackInputIsNull_ThrowsRestServiceException() {
      
        FeedbackRequestDTOV2 feedbackRequestDTO = new FeedbackRequestDTOV2("Class: {}, Method: {}, Object: {}",
                "Class: {}, Method: {}, Object: {}", "Class: {}, Method: {}, Object: {}", "Class: {}, Method: {}, Object: {}");

        ServicesStageFeedbackQuestionMappings servicesStageMappingsMock = Mockito.mock(ServicesStageFeedbackQuestionMappings.class);

  
        when(feedbackMapper.dtoToEntity(Mockito.any(FeedbackRequestDTOV2.class))).thenThrow(RestServiceException.class);


        assertThrows(RestServiceException.class,
                () -> feedbackServiceV2.createFeedback(feedbackRequestDTO, "channelName"),
                "Expected createFeedback to throw RestServiceException when feedbackMapper returns null");
    }

Can someone help me with what is wrong in the test case , why its not passing the mutation test.