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Testing BERT Tokenization Components in google-research/bert

This comprehensive test suite validates BERT’s tokenization functionality, covering both basic and WordPiece tokenization methods for multiple languages and character types. The tests ensure robust text preprocessing for BERT’s natural language processing tasks.

Test Coverage Overview

The test suite provides extensive coverage of BERT’s tokenization components:

Full tokenizer implementation testing with vocabulary handling
Chinese character tokenization verification
Case-sensitive and case-insensitive basic tokenization
WordPiece tokenizer functionality for subword tokenization
Token-to-ID conversion validation
Character type classification (whitespace, control, punctuation)

Implementation Analysis

The testing approach utilizes TensorFlow’s test framework with systematic validation of tokenization components:

Tests employ temporary file handling for vocabulary management and utilize Unicode character processing. The implementation follows a hierarchical pattern, testing from basic character-level operations to complete tokenization workflows.

Technical Details

Key technical components include:

TensorFlow test framework (tf.test.TestCase)
Python’s tempfile for temporary file operations
Unicode character handling for multi-language support
Custom vocabulary management
Python 2/3 compatibility handling

Best Practices Demonstrated

The test suite exemplifies several testing best practices:

Isolated test cases for each functionality
Comprehensive edge case handling
Clear test method naming conventions
Proper test setup and cleanup
Effective assertion usage for validation

google-research/bert

tokenization_test.py

            
# coding=utf-8
# Copyright 2018 The Google AI Language Team Authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

import os
import tempfile
import tokenization
import six
import tensorflow as tf


class TokenizationTest(tf.test.TestCase):

  def test_full_tokenizer(self):
    vocab_tokens = [
        "[UNK]", "[CLS]", "[SEP]", "want", "##want", "##ed", "wa", "un", "runn",
        "##ing", ","
    ]
    with tempfile.NamedTemporaryFile(delete=False) as vocab_writer:
      if six.PY2:
        vocab_writer.write("".join([x + "
" for x in vocab_tokens]))
      else:
        vocab_writer.write("".join(
            [x + "
" for x in vocab_tokens]).encode("utf-8"))

      vocab_file = vocab_writer.name

    tokenizer = tokenization.FullTokenizer(vocab_file)
    os.unlink(vocab_file)

    tokens = tokenizer.tokenize(u"UNwant\u00E9d,running")
    self.assertAllEqual(tokens, ["un", "##want", "##ed", ",", "runn", "##ing"])

    self.assertAllEqual(
        tokenizer.convert_tokens_to_ids(tokens), [7, 4, 5, 10, 8, 9])

  def test_chinese(self):
    tokenizer = tokenization.BasicTokenizer()

    self.assertAllEqual(
        tokenizer.tokenize(u"ah\u535A\u63A8zz"),
        [u"ah", u"\u535A", u"\u63A8", u"zz"])

  def test_basic_tokenizer_lower(self):
    tokenizer = tokenization.BasicTokenizer(do_lower_case=True)

    self.assertAllEqual(
        tokenizer.tokenize(u" \tHeLLo!how  
 Are yoU?  "),
        ["hello", "!", "how", "are", "you", "?"])
    self.assertAllEqual(tokenizer.tokenize(u"H\u00E9llo"), ["hello"])

  def test_basic_tokenizer_no_lower(self):
    tokenizer = tokenization.BasicTokenizer(do_lower_case=False)

    self.assertAllEqual(
        tokenizer.tokenize(u" \tHeLLo!how  
 Are yoU?  "),
        ["HeLLo", "!", "how", "Are", "yoU", "?"])

  def test_wordpiece_tokenizer(self):
    vocab_tokens = [
        "[UNK]", "[CLS]", "[SEP]", "want", "##want", "##ed", "wa", "un", "runn",
        "##ing"
    ]

    vocab = {}
    for (i, token) in enumerate(vocab_tokens):
      vocab[token] = i
    tokenizer = tokenization.WordpieceTokenizer(vocab=vocab)

    self.assertAllEqual(tokenizer.tokenize(""), [])

    self.assertAllEqual(
        tokenizer.tokenize("unwanted running"),
        ["un", "##want", "##ed", "runn", "##ing"])

    self.assertAllEqual(
        tokenizer.tokenize("unwantedX running"), ["[UNK]", "runn", "##ing"])

  def test_convert_tokens_to_ids(self):
    vocab_tokens = [
        "[UNK]", "[CLS]", "[SEP]", "want", "##want", "##ed", "wa", "un", "runn",
        "##ing"
    ]

    vocab = {}
    for (i, token) in enumerate(vocab_tokens):
      vocab[token] = i

    self.assertAllEqual(
        tokenization.convert_tokens_to_ids(
            vocab, ["un", "##want", "##ed", "runn", "##ing"]), [7, 4, 5, 8, 9])

  def test_is_whitespace(self):
    self.assertTrue(tokenization._is_whitespace(u" "))
    self.assertTrue(tokenization._is_whitespace(u"\t"))
    self.assertTrue(tokenization._is_whitespace(u"\r"))
    self.assertTrue(tokenization._is_whitespace(u"
"))
    self.assertTrue(tokenization._is_whitespace(u"\u00A0"))

    self.assertFalse(tokenization._is_whitespace(u"A"))
    self.assertFalse(tokenization._is_whitespace(u"-"))

  def test_is_control(self):
    self.assertTrue(tokenization._is_control(u"\u0005"))

    self.assertFalse(tokenization._is_control(u"A"))
    self.assertFalse(tokenization._is_control(u" "))
    self.assertFalse(tokenization._is_control(u"\t"))
    self.assertFalse(tokenization._is_control(u"\r"))
    self.assertFalse(tokenization._is_control(u"\U0001F4A9"))

  def test_is_punctuation(self):
    self.assertTrue(tokenization._is_punctuation(u"-"))
    self.assertTrue(tokenization._is_punctuation(u"$"))
    self.assertTrue(tokenization._is_punctuation(u"`"))
    self.assertTrue(tokenization._is_punctuation(u"."))

    self.assertFalse(tokenization._is_punctuation(u"A"))
    self.assertFalse(tokenization._is_punctuation(u" "))


if __name__ == "__main__":
  tf.test.main()