Mockito ClassCastException - A mock cannot be cast

Question

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
    }
}

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

My test looks like:

@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));
}

However I get the following error:

java.lang.ClassCastException: package.fruit.Fruit$$EnhancerByMockitoWithCGLIB$$b8254f54 cannot be cast to package.fruit.AppleFruit

which comes from this line in the test

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

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

score 49 · Accepted Answer · answered Feb 11 '15 at 19:25

When you say

@Mock
Fruit fruit;

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.

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

score 13 · Answer 2 · answered Jul 29 '21 at 11:47

13

To anyone searching for this just include:

@Mock(extraInterfaces = {AppleFruit.class})
Fruit fruit;

Which will add an extra interface to the mock and the casting wont raise any exceptions.

answered Jul 29 '21 at 11:47

Markus Ridziauskas

198
1
7

Juliano Suman Curti · Answer 3 · 2022-04-27T13:57:59.300

Mockito can deal with mocked objects that are already casted at mocking time (assignment). However, it does not cast by itself a mocked object during code execution.

In other words(or better yet, code):

Fruit fruit = Mockito.mock(Applefruit.class);

Just do as JB Nizet said and you will be fine. I had a similar problem and his solution worked.

For this question it would be:

@Mock
FruitBasket fruitBasket;

@Mock
AppleFruit fruit; // changed here

@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));
}

That is all what is needed.

score 1 · Answer 4 · answered Jul 21 '19 at 09:39

1

You can instruct mockito to return an object of subclass type, for a method which returns a super-class object. Then you won't need to tell mockito to cast the object.

answered Jul 21 '19 at 09:39

Siba Prasad Tripathy

73
4

3

An example of this would be very useful... Unless you mean simply declare it as AppleFruit... – jb62 Aug 27 '19 at 23:05

score 0 · Answer 5 · answered Feb 11 '15 at 19:24

0

Your mock object is enhanced by Mockito and it is not same as your class, so you can't type cast.

answered Feb 11 '15 at 19:24

Aninda Bhattacharyya

1,241
8
17

So is there not a way around it without not using a mock object? – user2844485 Feb 11 '15 at 19:24
3

There is definitely. I would suggest call the method with appleFruit instance, not fruit. – Aninda Bhattacharyya Feb 11 '15 at 19:28

Mockito ClassCastException - A mock cannot be cast

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