How do I use thenReturn for Class?

Question

This is a really newbie question but I don't know how to stub this.

I have to mock a method to return Class like this.

public Class<? extends SomeClass> getAClass();

if I do something like this

when(this.someInstance.getAClass())
    .thenReturn(SomeClassThatExtendsSomeClass.class);

I get compilation error.

The method thenReturn(Class<capture#1-of ? extends SomeClass>) in the type OngoingStubbing<Class<capture#1-of ? extends SomeClass>> is not applicable for the arguments (Class<SomeClassThatExtendsSomeClass>)

The method thenReturn(Class) in the type OngoingStubbing> is not applicable for the arguments (Class) — toy, Nov 12 '12 at 11:07
What does the definition of `SomeClassThatExtendsSomeClass` look like? — Anders R. Bystrup, Nov 12 '12 at 11:23

Vikdor · Accepted Answer · 2012-11-12T12:14:28.520

5

If the method declaration can be changed to what @Bohemian suggested above,

public <T extends SomeClass> Class<T> getAClass();

then you can write your mock statement as follows:

when(this.someInstance.<SomeClassThatExtendsSomeClass>getAClass())
     .thenReturn(SomeClassThatExtendsSomeClass.class);

Otherwise, the doReturn semantics should be used as follows:

Mockito
    .doReturn(SomeClassThatExtendsSomeClass.class)
    .when(this.someInstance.<SomeClassThatExtendsSomeClass>getAClass());

edited Nov 12 '12 at 12:14

answered Nov 12 '12 at 11:48

Vikdor

23,934
10
61
84

What if I can't change the method declaration? – toy Nov 12 '12 at 12:07
Then you should use the less type-safe `doReturn()` semantics to escape the compiler error while using `when().thenReturn()` semantics. – Vikdor Nov 12 '12 at 12:18

score 2 · Answer 2 · answered Nov 12 '12 at 12:14

If you can't change the method declaration so that it will work with thenReturn then you could use thenAnswer:

when(this.someInstance.getAClass()).thenAnswer(new Answer<Class<? extends SomeClass>>() {
            @Override
            public Class<? extends SomeClass> answer(InvocationOnMock invocation) throws Throwable {
                return SomeClassThatExtendsSomeClass.class;
            }
});

While it isn't ideal to do an implementation of Answer just to return a fixed value this should work for your scenario.

score 0 · Answer 3 · answered Nov 12 '12 at 11:30

0

Try typing the method:

public <T extends SomeClass> Class<T> getAClass();

when(this.someInstance.getAClass())
    .thenReturn(SomeClassThatExtendsSomeClass.class);

answered Nov 12 '12 at 11:30

Bohemian

412,405
93
575
722

Then the error is `thenReturn(Class) is not applicable for arguments Class`. – Vikdor Nov 12 '12 at 11:42

How do I use thenReturn for Class?

3 Answers3