无法用mockito模拟私有方法

我正试图用power mockito模拟一个私有方法,在阅读了这篇文章后,我有了一些想法,我遵循了相同的结构:

example

这是我的班级:

public class test(){
  private long verifyMarketEligibilityAndGetOfferDeliveryCalendar(long id)
  {
    some lins of code for connectiong to db
  }
  public long createOffer(long id){

    return verifyMarketEligibilityAndGetOfferDeliveryCalendar(id);
  }

}

这是我的模拟测试:

test classUnderTest = PowerMockito.spy(new test());
        PowerMockito.doReturn(10).when(classUnderTest,
                "verifyMarketEligibilityAndGetOfferDeliveryCalendar", 10l);
        classUnderTest.createOffer(10);

现在,我希望在调用createoffer之后,verifyMarketEqualityAndGetOfferDeliveryCalendar不会调用,而是返回数字10,但出于某种原因,程序会开始执行verifyMarketEquality AndGetOffer Deliverycalendar类,从而执行与数据库相关的代码。

有人能帮忙吗?