new_contents: # coding: utf8
  from __future__ import unicode_literals
  
  import pytest
  import regex as re
  
  from ...lang.en import English
  from ...tokenizer import Tokenizer
  
  
  @pytest.mark.xfail
  def test_issue1491():
      """Test possible off-by-one error in tokenizer prefix/suffix/infix rules."""
      prefix_re = re.compile(r'''[\[\("']''')
      suffix_re = re.compile(r'''[\]\)"']''')
      infix_re = re.compile(r'''[-~]''')
  
      def my_tokenizer(nlp):
          return Tokenizer(nlp.vocab, {},
                           prefix_search=prefix_re.search,
                           suffix_search=suffix_re.search,
                           infix_finditer=infix_re.finditer)
  
      nlp = English()
      nlp.tokenizer = my_tokenizer(nlp)
      doc = nlp("single quote 'goodbye end.")
      tokens = [token.text for token in doc]
      assert tokens == ['single', 'quote', "'", 'goodbye', 'end', '.']
  
subject: Add regression test for #1491