@Override
      public String explainFailure() throws IOException {
        final RegionStates regionStates =
          getMiniHBaseCluster().getMaster().getAssignmentManager().getRegionStates();
        return "found in transition: " + regionStates.getRegionsInTransition().toString();
      }
Returns a {@link Predicate} for checking that there are no regions in transition in master
hbase-server/src/test/java/org/apache/hadoop/hbase/HBaseTestingUtil.java