public void flushcache() throws IOException {
    for (JVMClusterUtil.RegionServerThread t : this.hbaseCluster.getRegionServers()) {
      for (HRegion r : t.getRegionServer().getOnlineRegionsLocalContext()) {
        executeFlush(r);
      }
    }
  }
Call flushCache on all regions on all participating regionservers.
hbase-server/src/test/java/org/apache/hadoop/hbase/SingleProcessHBaseCluster.java