@Override
    public Set<IndexSet> getAll() {
        return ImmutableSet.copyOf(findAllMongoIndexSets());
    }
@Test
    public void getAllShouldBeCachedForEmptyList() {
        final List<IndexSetConfig> indexSetConfigs = Collections.emptyList();
        when(indexSetService.findAll()).thenReturn(indexSetConfigs);

        assertThat(this.indexSetRegistry.getAll())
            .isNotNull()
            .isEmpty();

        assertThat(this.indexSetRegistry.getAll())
            .isNotNull()
            .isEmpty();

        verify(indexSetService, times(1)).findAll();
    }