message: check searcher num docs in proptest
diff: @@ -1436,6 +1436,8 @@ mod tests {
  let mut index_writer = index.writer_for_tests()?;
  index_writer.set_merge_policy(Box::new(NoMergePolicy));
  + let old_reader = index.reader()?;
  +
  for &op in ops {
  match op {
  IndexingOp::AddDoc { id } => {
  @@ -1474,6 +1476,21 @@ mod tests {
  assert!(index_writer.wait_merging_threads().is_ok());
  }
  }
  +
  + old_reader.reload()?;
  + let old_searcher = old_reader.searcher();
  +
  + let ids_old_searcher: HashSet<u64> = old_searcher
  + .segment_readers()
  + .iter()
  + .flat_map(|segment_reader| {
  + let ff_reader = segment_reader.fast_fields().u64(id_field).unwrap();
  + segment_reader
  + .doc_ids_alive()
  + .map(move |doc| ff_reader.get(doc))
  + })
  + .collect();
  +
  let ids: HashSet<u64> = searcher
  .segment_readers()
  .iter()
  @@ -1486,6 +1503,19 @@ mod tests {
  .collect();
  let (expected_ids_and_num_occurences, deleted_ids) = expected_ids(ops);
  + let num_docs_expected = expected_ids_and_num_occurences
  + .iter()
  + .map(|(_, id_occurences)| *id_occurences as usize)
  + .sum::<usize>();
  + assert_eq!(searcher.num_docs() as usize, num_docs_expected);
  + assert_eq!(old_searcher.num_docs() as usize, num_docs_expected);
  + assert_eq!(
  + ids_old_searcher,
  + expected_ids_and_num_occurences
  + .keys()
  + .cloned()
  + .collect::<HashSet<_>>()
  + );
  assert_eq!(
  ids,
  expected_ids_and_num_occurences
  