    @Test
    public void testCallBack(){

        when(mockList.get(Integer.MAX_VALUE)).thenAnswer(invocation -> {
            Object mock = invocation.getMock();
            Object[] arguments = invocation.getArguments();
            return new StringBuilder().append(mock).append(",").append(Arrays.asList(arguments)).toString();
        });

        System.out.println(mockList.get(Integer.MAX_VALUE));
        verify(mockList).get(Integer.MAX_VALUE);
    }