Not able to inject mock objects

I am newe to Mockito and Junit, I have written unit test cases for testing my rest service and made use of Mockito for injecting mocks. And code is below:

BillControllerTest.java:

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = Application.class)
@WebAppConfiguration
public class BillControllerTest{
private MockMvc mockMvc;

@Autowired
private WebApplicationContext webApplicationContext;

@InjectMocks
private BillController billController;

@Mock
private BillService mockBillService;

@Before
public void setupController() {
    MockitoAnnotations.initMocks(this);
    this.mockMvc = webAppContextSetup(webApplicationContext).build();
}


@Test
public void testBills() throws Exception {
    // some fake data
    final List<Bill> fakeBillList = new ArrayList<>();
    fakeBillList.add(CpsFake.bill("1234"));

    when(mockBillService.getBills(BILL_UID))
            .thenReturn(fakeBillList.stream());

    mockMvc.perform(get("/bills/" + BILL_UID ))
            .andExpect(content().contentType(MediaTypes.HAL_JSON))
                    // expect particular uid
            .andExpect(content().string(containsString("\"uid\":\"1234\"")))

ApplicationTest.java:

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = Application.class)
@WebAppConfiguration
public class ApplicationTest {

@Test
public void contextLoads() {
}

}

BillController.java:

@RestController
@RequestMapping(value = "/trials/{billUid}", produces = "application/hal+json")
public class BillController extends BaseController {
@Autowired
private BillService billService;

@Autowired
public BillController(BillService billService) {
    this.billService = billService;
}

@RequestMapping(method = RequestMethod.GET, value = "")
public ResponseEntity<Resources<Resource<Bill>>> getBills(@PathVariable String billUid) {
    return resourceListResponseEntity(
            () -> billService.getBills(billUid),
            bill-> createResource(bill),
            resources -> resources.add(linkTo(methodOn(BillController.class)
                    .getBills(billUid)).withSelfRel()));
}

When I run the test (BillControllerTest), mockBillService is not getting invoked and instead it is calling actual billService. Please help me in this issue. Thank you in advance.