private static UUID getRandomUUID() {
    return new UUID(ThreadLocalRandom.current().nextLong(), ThreadLocalRandom.current().nextLong());
  }
@return Where to write test data on local filesystem; usually
        {@link #DEFAULT_BASE_TEST_DIRECTORY} Should not be used by the unit tests, hence its's
        private. Unit test will use a subdirectory of this directory.
@see #setupDataTestDir()
hbase-diagnostics/src/main/java/org/apache/hadoop/hbase/util/WALPerformanceEvaluationUtil.java