Mockito when().thenReturn不必要地调用该方法 [英] Mockito when().thenReturn calls the method unnecessarily

问题描述

我正在研究继承的代码. 我编写了一个应该捕获NullPointerException的测试(因为它正在尝试从null对象调用方法)

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);

}

相关方法和变量:

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);
  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;
}

运行测试的jUnit结果是堆栈跟踪失败:

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

java.lang.Exception: Unexpected exception, expected<java.lang.NullPointerException> but was<org.mockito.exceptions.misusing.WrongTypeOfReturnValue>
Caused by: org.mockito.exceptions.misusing.WrongTypeOfReturnValue: 
Integer cannot be returned by getParameter()
getParameter() should return String#

我是否误解了when().thenReturn应该在这里工作的方式?我只希望getAction每次调用时都返回0，而getActionProduct返回null.显然，调用了getParameter()，我也不知道为什么.

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.

推荐答案

Mockito无法模拟静态方法.您的何时检查无效:

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

  when(BasketHelper.getAction(request)).thenReturn(0);
  when(BasketHelper.getActionProduct(site, request)).thenReturn(product);

这是我们要减少静态方法的使用的另一个原因，因为它很难模拟.

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

如果您的班级保持这种状态，那么没有简单的方法可以模拟行为.但是，如果要更改设计并使这两种方法都是非静态的.使用何时"的正确方法是对模拟对象应用检查.例如:

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);

但是，再次重申，这仅在​​您将类的getAction和getProduct方法重新设计为非静态时有效.

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

我记得还有其他一些测试框架确实支持模拟静态方法.

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

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