@Test
  public void testTableSkewCost() {
    Configuration conf = HBaseConfiguration.create();
    CostFunction costFunction = new TableSkewCostFunction(conf);
    for (int[] mockCluster : clusterStateMocks) {
      BalancerClusterState cluster = mockCluster(mockCluster);
      costFunction.prepare(cluster);
      double cost = costFunction.cost();
      assertTrue(cost >= 0);
      assertTrue(cost <= 1.01);
    }
  }
Data set for testLocalityCost: [test][0][0] = mapping of server to number of regions it hosts
[test][region + 1][0] = server that region is hosted on [test][region + 1][server + 1] =
locality for region on server
hbase-balancer/src/test/java/org/apache/hadoop/hbase/master/balancer/TestStochasticLoadBalancer.java