問題描述

我想測試 AppleProcessor 類中有一個方法:

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
    }
}

注意，Fruit 是 AppleFruit 實現的方法 getType() 的接口，并且還有一個 getApple() 方法.

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

我的測試看起來像:

@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));
}

但是我收到以下錯誤:

java.lang.ClassCastException: package.fruit.Fruit$$EnhancerByMockitoWithCGLIB$$b8254f54 無法轉換為 package.fruit.AppleFruit

來自測試中的這一行

when(((AppleFruit)fruit).getApple()).thenReturn(apple);

有人知道如何解決這個問題，以便我可以測試我的代碼嗎?

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

推薦答案

當你說

@Mock
Fruit fruit;

你告訴 Mockito:fruit 變量應該是 Fruit 的一個實例.Mockito會動態創建一個實現Fruit的類(這個類是Fruit$$EnhancerByMockitoWithCGLIB$$b8254f54)，并創建這個類的一個實例.這個類沒有理由成為 AppleFruit 的實例，因為您沒有告訴 Mockito 該對象必須是 AppleFruit 類型.

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.

將其聲明為AppleFruit，其類型為AppleFruit.

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

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