ArgumentCaptor为null

Question

我正在尝试为下面的代码编写单元测试，在这里我实例化一个bean并将其传递给类的其他私有方法以进行进一步处理，然后再执行main方法：

public OverviewTabViewBean build(Listing listing) {

   VehicleDetailListingBean vehicleDetailListingBean = new VehicleDetailListingBean();

   applyVehicleDetailListingRules(listing, vehicleDetailListingBean);
   OverviewTabViewBean overviewTabViewBean = new OverviewTabViewBean();

   if (vehicleDetailListingBean != null) {
        overviewTabViewBean.setMake(vehicleDetailListingBean.getMake());
        overviewTabViewBean.setModel(vehicleDetailListingBean.getModel());
      overviewTabViewBean.setAtCarId(vehicleDetailListingBean.getAtCarId());
   ..
   }

return overviewTabViewBean;

 private void applyCommonListingRules(Listing listing, VehicleDetailListingBean vehicleDetailListingBean) {
    rulesEngineService.applyRules(listing, vehicleDetailListingBean,   vehicleDetailRules.getCommonListingRules());
}

测试看起来像这样：

@Captor
ArgumentCaptor<OverviewTabViewBean> overviewTabViewBean;
@Captor
ArgumentCaptor<VehicleDetailListingBean> vehicleDetailListingBean;
@Mock
private RulesEngineService rulesEngineService;
@Mock
private VehicleDetailRules vehicleDetailRules;
@Mock
private VehicleReferenceService vehicleReferenceService;

@BeforeMethod
public void setUp() {
    MockitoAnnotations.initMocks(this);
}

/**
 * build
 */
@Test
public void build() {
    Listing listing = new Listing();
    listing.setListingId(111L);
    listing.setListingType(ListingType.NEW);

    List<Rule<Listing, ListingBean>> rules1 = new ArrayList<Rule<Listing, ListingBean>>();
    List<Rule<Listing, ListingBean>> rules2 = new ArrayList<Rule<Listing, ListingBean>>();
    doReturn(rules1).when(vehicleDetailRules).getCommonListingRules();
    doReturn(rules2).when(vehicleDetailRules).getDetailListingRules();

    overviewTabViewBeanBuilder.build(listing);
    verify(rulesEngineService, times(2)).applyRules(anyObject(), vehicleDetailListingBean.capture(), anyList());
    .....
    }

vehicleDetailListingBean 返回null并且不进入if块。我在这里做错了什么？