java when thenreturn,Mockito when().thenReturn不必要地调用该方法

た入场券 2023-01-24 04:23 6阅读 0赞

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I'm working a bit on an inherited code.

I've written a test that is supposed to catch NullPointerException (for it is trying to call a method from null object)

@Test(expected=NullPointerException.class)

public void checkXRequirement\_NullProduct\_AddAction\_ShouldThrowNullPointerException() throws CustomException \{

Site site = mock(Site.class);

Product product = null;

when(BasketHelper.getAction(request)).thenReturn(0);

when(BasketHelper.getActionProduct(site, request)).thenReturn(product);

BasketHelper.requiresX(request, site);

Relevant Methods and Variables:

public static final int ACTION\_ADD = 0;

public static final int ACTION\_DELETE = 1;

protected static int getAction(HttpServletRequest a\_request) \{

String sBuyProduct = a\_request.getParameter(ATTRIBUTE\_NAME\_BUY\_PRODUCT);

if (sBuyProduct != null) iAction = ACTION\_ADD;

else (sDelProduct != null) iAction = ACTION\_DELETE;

return iBasketAction

protected static Product getActionProduct(Site a\_site, HttpServletRequest a\_request) \{

String sBuyProduct = a\_request.getParameter(ATTRIBUTE\_NAME\_BUY\_PRODUCT);

String sDelProduct = a\_request.getParameter(ATTRIBUTE\_NAME\_DEL\_PRODUCT);

String sProduct = null;

switch (getBasketAction(a\_request)) \{

case BASKET\_ACTION\_ADD:

sProduct = sBuyProduct;

break;

case BASKET\_ACTION\_DELETE:

sProduct = sDelProduct;

break;

int iProductId;

try \{

iProductId = Integer.parseInt(sProduct);

\} catch (NumberFormatException nbrEx) \{

return null;

Product prod = getProductById(iProductId);

if (prod.isMasterProduct()) \{

prod = getChildProduct(prod, a\_site, a\_request);

return prod;

public static boolean requiresX(HttpServletRequest request, Site site) throws CustomException \{

try\{

if (getAction(request) == ACTION\_ADD) \{

Product prod = getActionProduct(site, request);

return prod.getType().isRequiredX();

\} catch(NullPointerException exception) \{

log.error("Error Message", exception);

return false;

The jUnit result of running the test is a failure with the stack trace of:

java.lang.Exception: Unexpected exception, expected but was

Caused by: org.mockito.exceptions.misusing.WrongTypeOfReturnValue:

Integer cannot be returned by getParameter()

getParameter() should return String\#

Do I misinterpret how when().thenReturn is supposed to work here? I just want getAction to return 0 and getActionProduct to return null whenever it's being called. Clearly getParameter() is called and I don't know why exactly.

解决方案

Mockito cannot mock static method. Your when check is not valid:

when(BasketHelper.getAction(request)).thenReturn(0);

when(BasketHelper.getActionProduct(site, request)).thenReturn(product);

That is another reason why we want to reduce the use of static method as it is hard to mock.

There is no easier way to mock the behavior if your class stays like this. However if you want to change your design and make both methods non-static. The correct way of using "when" is to apply the check on mocked object. For example:

BasketHelper basketHelper = mock(BasketHelper.class);

when(basketHelper.getAction(request)).thenReturn(0);

when(basketHelper.getActionProduct(site, request)).thenReturn(product);

But once again, this only work if you re-designed your class's getAction and getProduct method to be NON-STATIC.

I remember there are some other testing framework that does support mocking static method.

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