private RegionInfo getAndCheckSingleTableRegion(final List<HRegion> regions)
    throws IOException, InterruptedException {
    assertEquals(1, regions.size());
    RegionInfo hri = regions.get(0).getRegionInfo();
    AssignmentTestingUtil.waitForAssignment(cluster.getMaster().getAssignmentManager(), hri);
    return hri;
  }
The below tests are testing split region against a running cluster
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestSplitTransactionOnCluster.java