private void validateDescendingIterator(CloseableIterator iterator, int reverseStart,
      int reverseEnd) {
    for (int i = reverseStart; i > reverseEnd; i--) {
      IndexStoreEntry ise = (IndexStore.IndexStoreEntry) iterator.next();
      if (Integer.parseInt((String) ise.getDeserializedKey()) != i) {
        fail("descendingIterator did not return the expected reverse order");
      }
    }
  }
iterates through and checks against expected size
geode-core/src/integrationTest/java/org/apache/geode/cache/query/internal/index/MapIndexStoreJUnitTest.java