public static NamingSelector newClusterSelector(Collection<String> clusters) {
        if (CollectionUtils.isNotEmpty(clusters)) {
            final Set<String> set = new HashSet<>(clusters);
            Predicate<Instance> filter = instance -> set.contains(instance.getClusterName());
            String clusterString = getUniqueClusterString(clusters);
            return new ClusterSelector(filter, clusterString);
        } else {
            return EMPTY_SELECTOR;
        }
    }
@Test
    public void testNewClusterSelector2() {
        NamingSelector namingSelector1 = NamingSelectorFactory.newClusterSelector(Arrays.asList("a", "b", "c"));
        NamingSelector namingSelector2 = NamingSelectorFactory.newClusterSelector(Arrays.asList("c", "b", "a"));
        NamingSelector namingSelector3 = NamingSelectorFactory.newClusterSelector(Arrays.asList("a", "b", "c", "c"));
        NamingSelector namingSelector4 = NamingSelectorFactory.newClusterSelector(Arrays.asList("d", "e"));
        
        assertEquals(namingSelector1, namingSelector2);
        assertEquals(namingSelector1, namingSelector3);
        assertNotEquals(namingSelector1, namingSelector4);
    }