DirectoryReader reader2 = DirectoryReader.open(dir2);
assertEquals(1, reader1.maxDoc());
assertEquals(1, reader2.maxDoc());
assertEquals(1, reader1.numDocs());
assertEquals(1, reader2.numDocs());
Document document1 = reader1.document(0);
Document document2 = reader2.document(0);
assertEquals(document1.get("id"), document2.get("id"));