Spring Factory Design Pattern Unit Test

I have a factory design pattern which returns particular service according to the enum type and it works perfectly when I run the application but factory throws error on unit test.

@Service
public class GaServiceFactory {

    @Autowired
    private ApplicationContext appContext;

    public IGaService getInstance(GaType type) {

        if (MAN.equals(type)) {
            return appContext.getBean(ManGaService.class);
        }

        throw new RuntimeException("No matching service could be created");
    }

}

Here's my controller class;

@RestController
@RequestMapping(GA)
public class GaController {

    @Autowired
    private GaServiceFactory factory;

    @PostMapping(value = INITIALIZE, produces = APPLICATION_JSON_VALUE)
    public ResponseEntity<GaDTO> initialize() {
        return status(CREATED).body(factory.getInstance(MAN).initialize());
    }

And here's my unit test;

@WebMvcTest(value = GaController.class)
class GaControllerTest {

    @Autowired
    private MockMvc mockMvc;

    @MockBean
    private GaServiceFactory factory;

    @Mock
    private ApplicationContext appContext;

    private GaDTO gaDTO;

    private List<GaDTO> gaDTOList;

    @BeforeEach
    void setUp() {
        gaDTOList= new ArrayList<>();
        Ga ga = new Ga();
        gaDTO = new GaDTO();
        gaDTO.setId(ga.getId());
        gaDTOList.add(gaDTO);
    }

    @Test
    public void initialize_success() throws Exception {
        when(factory.getInstance(MAN).initialize()).thenReturn(gaDTO);

        mockMvc.perform(post(GA + INITIALIZE)
                        .contentType(APPLICATION_JSON))
                .andExpect(status().isCreated())
                .andExpect(jsonPath("$.id", is(gaDTO.getId())));
    }

ApplicationContext in the factory returns null and it throws an error when I expect the initialize method in the service to work. How can I mock the factory to work as expected.