protected static void setupClusterTestDir() {
    // Using randomUUID ensures that multiple clusters can be launched by
    // a same test, if it stops & starts them
    Path testDir =
      UTIL.getDataTestDir("cluster_" + HBaseCommonTestingUtil.getRandomUUID().toString());
    CLUSTER_TEST_DIR = new File(testDir.toString()).getAbsoluteFile();
    // Have it cleaned up on exit
    boolean b = deleteOnExit();
    if (b) {
      CLUSTER_TEST_DIR.deleteOnExit();
    }
    LOG.info("Created new mini-cluster data directory: {}, deleteOnExit={}", CLUSTER_TEST_DIR, b);
  }
Creates a directory for the cluster, under the test data
hbase-asyncfs/src/test/java/org/apache/hadoop/hbase/io/asyncfs/AsyncFSTestBase.java