.. Copyright (C) 2001-2021 NLTK Project
.. For license information, see LICENSE.TXT

Regression Tests
~~~~~~~~~~~~~~~~

Sequential Taggers
------------------

Add tests for:
  - make sure backoff is being done correctly.
  - make sure ngram taggers don't use previous sentences for context.
  - make sure ngram taggers see 'beginning of the sentence' as a
    unique context
  - make sure regexp tagger's regexps are tried in order
  - train on some simple examples, & make sure that the size & the
    generated models are correct.
  - make sure cutoff works as intended
  - make sure that ngram models only exclude contexts covered by the
    backoff tagger if the backoff tagger gets that context correct at
    *all* locations.


Regression Testing for issue #1025
==================================

We want to ensure that a RegexpTagger can be created with more than 100 patterns
and does not fail with:
 "AssertionError: sorry, but this version only supports 100 named groups"

    >>> from nltk.tag import RegexpTagger
    >>> patterns = [(str(i), 'NNP',) for i in range(200)]
    >>> tagger = RegexpTagger(patterns)

Regression Testing for issue #2483
==================================

Ensure that tagging with pos_tag (PerceptronTagger) does not throw an IndexError
when attempting tagging an empty string. What it must return instead is not
strictly defined.

    >>> from nltk.tag import pos_tag
    >>> pos_tag(['', 'is', 'a', 'beautiful', 'day'])
    [...]