@Override
    protected boolean isSelectable(InstancesChangeEvent event) {
        return event != null && event.getHosts() != null && event.getInstancesDiff() != null;
    }
@Test
    public void testSelectable() {
        NamingSelectorWrapper selectorWrapper = new NamingSelectorWrapper(null, null);
        assertFalse(selectorWrapper.isSelectable(null));
        InstancesChangeEvent event1 = new InstancesChangeEvent(null, null, null, null, null, null);
        assertFalse(selectorWrapper.isSelectable(event1));
        InstancesChangeEvent event2 = new InstancesChangeEvent(null, null, null, null, null, new InstancesDiff());
        assertFalse(selectorWrapper.isSelectable(event2));
        InstancesChangeEvent event3 = new InstancesChangeEvent(null, null, null, null, Collections.emptyList(), null);
        assertFalse(selectorWrapper.isSelectable(event3));
        InstancesChangeEvent event4 = new InstancesChangeEvent(null, null, null, null, Collections.emptyList(),
                new InstancesDiff());
        assertTrue(selectorWrapper.isSelectable(event4));
    }