@Test
    void unstable_init_storage_node_has_init_state_substituted_by_down() {
        final ClusterFixture fixture = ClusterFixture.forFlatCluster(5)
                .bringEntireClusterUp()
                .reportStorageNodeState(0, State.INITIALIZING)
                .reportStorageNodeState(0, State.DOWN) // Init -> Down triggers unstable init flag
                .reportStorageNodeState(0, new NodeState(NodeType.STORAGE, State.INITIALIZING).setInitProgress(0.5f));

        final AnnotatedClusterState state = generateFromFixtureWithDefaultParams(fixture);
        assertThat(state.toString(), equalTo("distributor:5 storage:5 .0.s:d"));
    }
Legacy behavior: if a node has crashed (i.e. transition into Down) at least once
while in Init mode, its subsequent init mode will not be made public.
This means the node will remain in a Down-state until it has finished
initializing. This is presumably because unstable nodes may not be able to finish
their init stage and would otherwise pop in and out of the cluster state.
clustercontroller-core/src/test/java/com/yahoo/vespa/clustercontroller/core/ClusterStateGeneratorTest.java