public Set<Integer> nodesThatShouldBeDown(ClusterState state) {
        return calculate(state).nodesThatShouldBeDown();
    }
@Test
    void down_to_down_edge_keeps_group_down() {
        GroupAvailabilityCalculator calc = calcForHierarchicCluster(
                DistributionBuilder.withGroups(2).eachWithNodeCount(4), 0.76);

        assertThat(calc.nodesThatShouldBeDown(clusterState(
                "distributor:8 storage:8 .1.s:d")), equalTo(indices(0, 2, 3)));

        assertThat(calc.nodesThatShouldBeDown(clusterState(
                "distributor:8 storage:8 .1.s:d .2.s:d")), equalTo(indices(0, 3)));
    }