@Override
    public DiscreteResources difference(DiscreteResources other) {
        return this;
    }
@Test
    public void testDifference() {
        DiscreteResource res1 = Resources.discrete(DeviceId.deviceId("a")).resource();
        DiscreteResource res2 = Resources.discrete(DeviceId.deviceId("b")).resource();

        assertThat(sut.difference(DiscreteResources.of(ImmutableSet.of(res1))),
                is(EmptyDiscreteResources.INSTANCE));
        assertThat(sut.difference(DiscreteResources.of(ImmutableSet.of(res2))),
                is(EmptyDiscreteResources.INSTANCE));
    }