Mockito mock another class function

How to mock function from another class with Mockito? Example:

public class MyClass extends BaseClass {
    Data initData();
}

public abstract class BaseClass {
 public Data initData() {
        return ((Data) this.getArguments());
    }
} 

Mockito:

   @Test
    public void testInitData() throws Exception {
        Data data;
        data = MyClass.initData();
        System.out.println(data);
        assertNotNull(data);
    }

And then result is always null. Do I miss something?