private Object getDiskBytes(PartitionedRegion pr) {
    Set<BucketRegion> brs = pr.getDataStore().getAllLocalBucketRegions();

    long bytes = 0;
    for (BucketRegion br : brs) {
      bytes += br.getNumOverflowBytesOnDisk();
    }

    return bytes;
  }
This test verifies that PR statistics are working properly for single/multiple
PartitionedRegions on single node.
geode-core/src/integrationTest/java/org/apache/geode/internal/cache/PartitionedRegionStatsJUnitTest.java