How to do integrating test in a spring MVC controller which has factory method?

I have a spring controller which has outter environment dependency in the requesting mapping method and the dependency was intruduced by a factory single-instance method:

@RequestMapping(path = "/video_course", method = RequestMethod.POST)
  public JSONObject createVideoCourse(@RequestBody @Valid VideoCourseDTO dto,
      HttpServletRequest request) {
    try {
      ContextManagerFactory.getInstance().setContext(request); // How to mock the ContextManagerFactory in unit testing?
      Context ctx = ContextManagerFactory.getInstance().getContext();
      Course course = ctx.getCourse();
      Content parentContent = ctx.getContent();

      long id = videoCourseService.addVideoCourse(dto.title, dto.available,
          String.join(",", dto.keywords), dto.videos, course, parentContent, dto.tracking);
      JSONObject json = new JSONObject();
      json.put("vc_id", id);
      return json;

    } catch (Exception e) {
      logger.error("createVideoCourse", e);
      throw new ServerInternalException(e.getMessage());
    }
  }

With the following junit test case:

@RunWith(SpringRunner.class)
@WebAppConfiguration
@ContextConfiguration(classes = {SpringMvcTestConfig.class, HibernateDevConfig.class,
    BlackboardEnvironmentConfig.class, VideoRepoTestConfig.class, VideoCourseTestConfig.class})
@Sql("classpath:video_course.sql")
@Transactional
@ActiveProfiles("dev")
public class VideoCourseApiTest {

  private static Logger logger = LoggerFactory.getLogger(VideoCourseApiTest.class);

  @Autowired
  private WebApplicationContext wac;

  private MockMvc mockMvc;

  @Before
  public void setup() {
    this.mockMvc = MockMvcBuilders.webAppContextSetup(this.wac).build();
  }

  @Test
  public void testCreateVideoCourse() throws Exception {
    JSONObject json = new JSONObject();
    // construct the request body json string ...
    logger.debug("request body: \n{}",json.toJSONString());
    mockMvc
        .perform(post("/course/video_course").content(json.toJSONString())
            .contentType(MediaType.APPLICATION_JSON))
        .andDo(print()).andExpect(status().isOk()).andExpect(jsonPath("vc_id", is(greaterThan(0))));
  }

}

And I don't know how to mock the ContextManagerFactory with Mockito in such situation. Anyone could help me? Thanks.