MockitoException - 是一个*void方法*,它*不能用*返回值*来存根!

Question

我正在使用Mockito进行单元测试,我得到以下异常.

org.mockito.exceptions.base.MockitoException: 
`'setResponseTimeStampUtc'` is a *void method* and it *cannot* be stubbed with a *return value*!
Voids are usually stubbed with Throwables:
    doThrow(exception).when(mock).someVoidMethod();
***

If you're unsure why you're getting above error read on.
Due to the nature of the syntax above problem might occur because:
1. The method you are trying to stub is *overloaded*. Make sure you are calling the right overloaded version.
2. Somewhere in your test you are stubbing *final methods*. Sorry, Mockito does not verify/stub final methods.
3. A spy is stubbed using `when(spy.foo()).then()` syntax. It is safer to stub spies - 
   - with `doReturn|Throw()` family of methods. More in javadocs for Mockito.spy() method.

这是实际的课程

@Repository
public class CardRepositoryImpl implements ICardRepository {        
    @Autowired
    private OperationBean operation;

    @Override
    public OperationBean getCardOperation(final String cardHolderId, final String requestTimeStamp) {
        operation.setRequestTimeStampUtc(requestTimeStamp);
        operation.setResponseTimeStampUtc(DateUtil.getUTCDate());
        return operation;
    }
}

这是我写过的Test课程.

@RunWith(MockitoJUnitRunner.class)
public class CardRepositoryImplUnitTestFixture_Mockito {
    @InjectMocks
    private CardRepositoryImpl cardRepositoryImpl;
    private OperationBean operationBean;

    @Before
    public void beforeTest() {
        MockitoAnnotations.initMocks(this);
    }
    @Test
    public void canGetCardOperation(){
        when(cardRepositoryImpl.getCardOperation("2", Mockito.anyString())).thenReturn(operationBean);

    }    
}

这是return语句的问题,因为format()方法是最终方法.

public static String getUTCDate() {
    final TimeZone timeZone = TimeZone.getTimeZone("UTC");
    final Calendar calendar = Calendar.getInstance(timeZone);
    final SimpleDateFormat simpleDateFormat = new SimpleDateFormat("YYYY-MM-dd'T'HH:mm:ss.SSS'Z'");
    simpleDateFormat.setTimeZone(timeZone);
    return simpleDateFormat.format(calendar.getTime());
}

我该如何解决这个问题？

Answer 1

@InjectMocks
private CardRepositoryImpl cardRepositoryImpl;

when(cardRepositoryImpl.getCardOperation("2", Mockito.anyString()))
    .thenReturn(operationBean);

cardRepositoryImpl不是模拟，所以你不能存根。随着@InjectMocks你指示的Mockito构建一个真正的CardRepositoryImpl，并有自己的私人领域，并与测试用例领域取代构造函数的参数。你可能想改用间谍；稍后会详细介绍。

但首先，为什么会出现该错误消息？因为它不是模拟，所以调用cardRepositoryImpl.getCardOperation发生在实际的 CardRepositoryImpl 实例上。Mockito 看到与operationBean（似乎是模拟）的交互，将when和thenReturn视为与最近的模拟调用相对应，并错误地告诉您您正在使用返回值存根 void 方法（重要的是，错误的方法）。

在 CardRepositoryImpl 的测试中，您不应该模拟 CardRepositoryImpl，也不应该对其进行存根以返回值：这不会测试任何东西，除了 Mockito 可以工作。您可能应该重新考虑为了让您的测试工作需要存根什么。

但是，当存根一个方法时，您可能希望存根同一个类中的另一个方法。这可以通过间谍来完成：

@Test
public void canGetCardOperation(){
    CardRepositoryImpl spyImpl = spy(cardRepositoryImpl);
    when(spyImpl.getCardOperation(Mockito.eq("2"), Mockito.anyString()))
        .thenReturn(returnValue);
    // ...
    spyImpl.someOtherMethod();  // Any matching calls to getCardOperation from
                                // someOtherMethod will use the stub above.
}

旁注：您在存根时相邻地使用anyString和"2"。使用 Matchers like 时anyString，如果您将它们用于任何参数，则需要将它们用于所有参数。在这里查看更多。