private void assertDistinctParentHosts(NodeList nodes, ClusterSpec.Type clusterType, int expectedCount) {
        Set<String> parentHosts = hostsOf(nodes, Optional.of(clusterType));
        assertEquals(expectedCount, parentHosts.size());
    }
Non-exclusive app first, then an exclusive: Should give the same result as above
node-repository/src/test/java/com/yahoo/vespa/hosted/provision/provisioning/VirtualNodeProvisioningTest.java