@InjectMocks isnt actually injecting mocks

So i have a class that needs to be tested. Lets call it ClassToTest. It has a couple of Dao objects as fields.

Public class ClassToTest {

    @Autowired
    MyDao dao;

    void methodToTest() {
        dao.save(something);
    }
}

As you can see ClassToTest does not contain any constructor or setter and I am using spring to autowire the fields.

Now, I have a base test class with all the dependencies that classToTest requires:

public abstract BaseTest {

    @Mock
    MyDao dao;

}

And the testClass extends this BaseTest class :

public class TestClass extends BaseTest {

    @InjectMocks
    ClassToTest classToTest = new ClassToTest();

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

    @Test
    public void test() {
        classToTest.methodToTest();
    }
}

This results in a null pointer exception when the save happens. However, if i change setup method to this :

@Before 
public void setup() {
    MockitoAnnotations.initMocks(this);
    classToTest.dao = dao;
}

the test passes.

My understanding was that when a class does not have a constructor or a setter, InjectMocks would inject the mocks by using field injection. Why is that not happening here?