private void executeAndValidateQueryResults(String queryString) {
    Query query = getCache().getQueryService().newQuery(queryString);
    // Now run the query
    SelectResults results = null;
    for (int i = 0; i < 50; i++) {
      try {
        logger.debug("Querying the region");
        results = (SelectResults) query.execute();
      } catch (Exception e) {
        e.printStackTrace();
        logger.error("Query Execution failed", e);
        fail();
      }
      for (Object obj : results) {
        if (obj instanceof Undefined) {
          fail("Found an undefined element" + Arrays.toString(results.toArray()));
        }
      }
    }
  }
Test creates a local region. Creates and removes index in a parallel running thread. Then
destroys and puts back entries in separated thread in the same region and runs query in parallel
and checks for UNDEFINED values in result set of the query.
geode-core/src/distributedTest/java/org/apache/geode/cache/query/internal/index/InitializeIndexEntryDestroyQueryDUnitTest.java