@Override
    public Collection<String> childNames() {
        ArrayList<String> childNames = new ArrayList<>();
        for (Integer brokerId : image.brokers().keySet()) {
            childNames.add(brokerId.toString());
        }
        return childNames;
    }
@Test
    public void testChildNames() {
        assertEquals(Collections.singletonList("1"), NODE.childNames());
    }