public HRegion createTestRegion(String tableName, ColumnFamilyDescriptor cd,
    BlockCache blockCache) throws IOException {
    TableDescriptor td =
      TableDescriptorBuilder.newBuilder(TableName.valueOf(tableName)).setColumnFamily(cd).build();
    RegionInfo info = RegionInfoBuilder.newBuilder(TableName.valueOf(tableName)).build();
    return createRegionAndWAL(info, getDataTestDir(), getConfiguration(), td, blockCache);
  }
Check to make sure the region is open on the specified region server, but not on any other one.
hbase-server/src/test/java/org/apache/hadoop/hbase/HBaseTestingUtil.java