@Test
  public void testRandom() throws Exception {
    Directory directory = newDirectory();
    final Random r = random();
    final IndexWriterConfig iwc =
        LuceneTestCase.newIndexWriterConfig(r, new MockAnalyzer(r))
            .setMaxBufferedDocs(IndexWriterConfig.DISABLE_AUTO_FLUSH)
            .setRAMBufferSizeMB(
                scaledRandomIntBetween(16, 64)); // we might index a lot - don't go crazy here
    RandomIndexWriter indexWriter = new RandomIndexWriter(r, directory, iwc);
    int numUniqueChildValues = scaledRandomIntBetween(100, 2000);
    String[] childValues = new String[numUniqueChildValues];
    for (int i = 0; i < numUniqueChildValues; i++) {
      childValues[i] = Integer.toString(i);
    }

    IntOpenHashSet filteredOrDeletedDocs = new IntOpenHashSet();
    int childDocId = 0;
    int numParentDocs = scaledRandomIntBetween(1, numUniqueChildValues);
    ObjectObjectOpenHashMap<String, NavigableSet<String>> childValueToParentIds =
        new ObjectObjectOpenHashMap<>();
    for (int parentDocId = 0; parentDocId < numParentDocs; parentDocId++) {
      boolean markParentAsDeleted = rarely();
      boolean filterMe = rarely();
      String parent = Integer.toString(parentDocId);
      Document document = new Document();
      document.add(
          new StringField(UidFieldMapper.NAME, Uid.createUid("parent", parent), Field.Store.YES));
      document.add(new StringField(TypeFieldMapper.NAME, "parent", Field.Store.NO));
      if (markParentAsDeleted) {
        filteredOrDeletedDocs.add(parentDocId);
        document.add(new StringField("delete", "me", Field.Store.NO));
      }
      if (filterMe) {
        filteredOrDeletedDocs.add(parentDocId);
        document.add(new StringField("filter", "me", Field.Store.NO));
      }
      indexWriter.addDocument(document);

      final int numChildDocs = scaledRandomIntBetween(0, 100);
      for (int i = 0; i < numChildDocs; i++) {
        boolean markChildAsDeleted = rarely();
        String childValue = childValues[random().nextInt(childValues.length)];

        document = new Document();
        document.add(
            new StringField(
                UidFieldMapper.NAME,
                Uid.createUid("child", Integer.toString(childDocId++)),
                Field.Store.NO));
        document.add(new StringField(TypeFieldMapper.NAME, "child", Field.Store.NO));
        document.add(
            new StringField(
                ParentFieldMapper.NAME, Uid.createUid("parent", parent), Field.Store.NO));
        document.add(new StringField("field1", childValue, Field.Store.NO));
        if (markChildAsDeleted) {
          document.add(new StringField("delete", "me", Field.Store.NO));
        }
        indexWriter.addDocument(document);

        if (!markChildAsDeleted) {
          NavigableSet<String> parentIds;
          if (childValueToParentIds.containsKey(childValue)) {
            parentIds = childValueToParentIds.lget();
          } else {
            childValueToParentIds.put(childValue, parentIds = new TreeSet<>());
          }
          if (!markParentAsDeleted && !filterMe) {
            parentIds.add(parent);
          }
        }
      }
    }

    // Delete docs that are marked to be deleted.
    indexWriter.deleteDocuments(new Term("delete", "me"));

    indexWriter.commit();
    IndexReader indexReader = DirectoryReader.open(directory);
    IndexSearcher searcher = new IndexSearcher(indexReader);
    Engine.Searcher engineSearcher =
        new Engine.Searcher(ChildrenConstantScoreQueryTests.class.getSimpleName(), searcher);
    ((TestSearchContext) SearchContext.current())
        .setSearcher(new ContextIndexSearcher(SearchContext.current(), engineSearcher));

    int max = numUniqueChildValues / 4;
    for (int i = 0; i < max; i++) {
      // Simulate a parent update
      if (random().nextBoolean()) {
        final int numberOfUpdatableParents = numParentDocs - filteredOrDeletedDocs.size();
        int numberOfUpdates = scaledRandomIntBetween(0, numberOfUpdatableParents);
        for (int j = 0; j < numberOfUpdates; j++) {
          int parentId;
          do {
            parentId = random().nextInt(numParentDocs);
          } while (filteredOrDeletedDocs.contains(parentId));

          String parentUid = Uid.createUid("parent", Integer.toString(parentId));
          indexWriter.deleteDocuments(new Term(UidFieldMapper.NAME, parentUid));

          Document document = new Document();
          document.add(new StringField(UidFieldMapper.NAME, parentUid, Field.Store.YES));
          document.add(new StringField(TypeFieldMapper.NAME, "parent", Field.Store.NO));
          indexWriter.addDocument(document);
        }

        indexReader.close();
        indexReader = DirectoryReader.open(indexWriter.w, true);
        searcher = new IndexSearcher(indexReader);
        engineSearcher =
            new Engine.Searcher(ChildrenConstantScoreQueryTests.class.getSimpleName(), searcher);
        ((TestSearchContext) SearchContext.current())
            .setSearcher(new ContextIndexSearcher(SearchContext.current(), engineSearcher));
      }

      String childValue = childValues[random().nextInt(numUniqueChildValues)];
      int shortCircuitParentDocSet = random().nextInt(numParentDocs);
      QueryBuilder queryBuilder;
      if (random().nextBoolean()) {
        queryBuilder =
            hasChildQuery("child", termQuery("field1", childValue))
                .setShortCircuitCutoff(shortCircuitParentDocSet);
      } else {
        queryBuilder =
            constantScoreQuery(
                hasChildFilter("child", termQuery("field1", childValue))
                    .setShortCircuitCutoff(shortCircuitParentDocSet));
      }
      // Using a FQ, will invoke / test the Scorer#advance(..) and also let the Weight#scorer not
      // get live docs as acceptedDocs
      queryBuilder = filteredQuery(queryBuilder, notFilter(termFilter("filter", "me")));
      Query query = parseQuery(queryBuilder);

      BitSetCollector collector = new BitSetCollector(indexReader.maxDoc());
      searcher.search(query, collector);
      FixedBitSet actualResult = collector.getResult();

      FixedBitSet expectedResult = new FixedBitSet(indexReader.maxDoc());
      if (childValueToParentIds.containsKey(childValue)) {
        LeafReader slowLeafReader = SlowCompositeReaderWrapper.wrap(indexReader);
        Terms terms = slowLeafReader.terms(UidFieldMapper.NAME);
        if (terms != null) {
          NavigableSet<String> parentIds = childValueToParentIds.lget();
          TermsEnum termsEnum = terms.iterator(null);
          PostingsEnum docsEnum = null;
          for (String id : parentIds) {
            TermsEnum.SeekStatus seekStatus =
                termsEnum.seekCeil(Uid.createUidAsBytes("parent", id));
            if (seekStatus == TermsEnum.SeekStatus.FOUND) {
              docsEnum =
                  termsEnum.postings(slowLeafReader.getLiveDocs(), docsEnum, PostingsEnum.NONE);
              expectedResult.set(docsEnum.nextDoc());
            } else if (seekStatus == TermsEnum.SeekStatus.END) {
              break;
            }
          }
        }
      }

      assertBitSet(actualResult, expectedResult, searcher);
    }

    indexWriter.close();
    indexReader.close();
    directory.close();
  }