public static WAL createWal(final Configuration conf, final Path rootDir, final RegionInfo hri)
    throws IOException {
    // The WAL subsystem will use the default rootDir rather than the passed in rootDir
    // unless I pass along via the conf.
    Configuration confForWAL = new Configuration(conf);
    confForWAL.set(HConstants.HBASE_DIR, rootDir.toString());
    return new WALFactory(confForWAL, "hregion-" + RandomStringUtils.randomNumeric(8)).getWAL(hri);
  }
Create an unmanaged WAL. Be sure to close it when you're through.
hbase-testing-util/src/main/java/org/apache/hadoop/hbase/HBaseTestingUtility.java