@AfterClass
  public static void after() throws IOException {
    // Clean everything up.
    util.restoreCluster();
    util = null;

    // Stop the threads so that we know everything is complete.
    executorService.shutdown();
    executorService = null;

    // Clean up the actions.
    moveRegionAction = null;
    restartMetaAction = null;
    moveMetaRegionsAction = null;
    restartRSAction = null;
    restartMasterAction = null;

    loadTool = null;
  }
The load test tool used to create load and make sure that WALs aren't empty.
hbase-it/src/test/java/org/apache/hadoop/hbase/mttr/IntegrationTestMTTR.java