assertEquals(1, clusters.get(0).size());
assertEquals(2, clusters.get(1).size());
assertEquals(3, clusters.get(2).size());
assertEquals(6, clusters.get(3).size());
ClusterNode clusterNode = clusters.get(0).get(0);
traverse(clusterNode, 0, result);
// check if all our points were in the right cluster levels
assertEquals(0, result.size());
}