Mockito ClassCastException - 无法强制转换模拟 [英] Mockito ClassCastException - A mock cannot be cast

问题描述

我在类 AppleProcessor 中有一个方法，我想测试一下：

I have a method in the class AppleProcessor which I would like to test:

public void process(Fruit fruit) {
    if(fruit.getType() == Fruit.APPLE) {
        fruitBasket.add(((AppleFruit) fruit).getApple());
    }
    else {
        // do something else
    }
}

请注意，Fruit是AppleFruit实现的方法 getType（）的接口，并且还有 getApple（） 方法。

Note that Fruit is an interface with the method getType() which AppleFruit implements and also has a getApple() method.

我的测试如下：

@Mock
FruitBasket fruitBasket;

@Mock
Fruit fruit;

@Mock
AppleFruit apple;

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

@Test
public void testAnAppleIsProcessed() {
    AppleProcessor appleProcessor = new AppleProcessoer();
    when(fruit.getType()).thenReturn(Fruit.APPLE);
    when(((AppleFruit) fruit).getApple()).thenReturn(apple);

    appleProcessor.process(fruit);

    verify(fruitBasket).add(isA(Apple.class));
}

但是我收到以下错误：

java.lang.ClassCastException：package.fruit.Fruit $$ EnhancerByMockitoWithCGLIB $$ b8254f54无法强制转换为package.fruit.AppleFruit

来自测试中的这一行

何时（（（AppleFruit）水果）.getApple（ ））。thenReturn（apple）;

有谁知道如何解决这个问题，以便我可以测试我的代码？

Would anyone know how to resolve this so I can test my code?

推荐答案

当你说

@Mock
Fruit fruit;

你告诉Mockito： fruit 变量应该是是 Fruit 的一个实例。 Mockito将动态创建一个实现 Fruit 的类（此类为 Fruit $$ EnhancerByMockitoWithCGLIB $$ b8254f54 ），并创建这个类的一个实例。这个类没有理由成为 AppleFruit 的实例，因为你没有告诉Mockito该对象必须是AppleFruit类型。

You tell Mockito: the fruit variable should be an instance of Fruit. Mockito will dynamically create a class which implements Fruit (this class is Fruit$$EnhancerByMockitoWithCGLIB$$b8254f54), and create an instance of this class. There's no reason for this class to be an instance of AppleFruit, since you didn't tell Mockito that the object had to be of type AppleFruit.

将其声明为 AppleFruit ，它的类型为 AppleFruit 。

Declare it as AppleFruit, and it will be of type AppleFruit.

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