@Before
  public void before() throws IOException {
    // New rules file name per test.
    this.rulesFilename =
      HTU.getDataTestDir(this.name.getMethodName() + "." + DEFAULT_RULES_FILE_NAME).toString();
    // Set the created rules filename into the configuration.
    HTU.getConfiguration().set(
      HeterogeneousRegionCountCostFunction.HBASE_MASTER_BALANCER_HETEROGENEOUS_RULES_FILE,
      this.rulesFilename);
  }
Make a file for rules that is inside a temporary test dir named for the method so it doesn't
clash w/ other rule files.
hbase-balancer/src/test/java/org/apache/hadoop/hbase/master/balancer/TestStochasticLoadBalancerHeterogeneousCostRules.java