text: # Copyright 2017 The Abseil 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.
  
  """Base functionality for Abseil Python tests.
  
  This module contains base classes and high-level functions for Abseil-style
  tests.
  """
  
  from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  
  import contextlib
  import difflib
  import errno
  import getpass
  import inspect
  import io
  import itertools
  import json
  import os
  import random
  import re
  import shlex
  import shutil
  import signal
  import stat
  import subprocess
  import sys
  import tempfile
  import textwrap
  import unittest
  
  try:
    # The faulthandler module isn't always available, and pytype doesn't
    # understand that we're catching ImportError, so suppress the error.
    # pytype: disable=import-error
    import faulthandler
    # pytype: enable=import-error
  except ImportError:
    # We use faulthandler if it is available.
    faulthandler = None
  
  from absl import app
  from absl import flags
  from absl import logging
  from absl._collections_abc import abc
  from absl._enum_module import enum
  from absl.testing import _pretty_print_reporter
  from absl.testing import xml_reporter
  from absl.third_party import unittest3_backport
  import six
  from six.moves import urllib
  from six.moves import xrange  # pylint: disable=redefined-builtin
  
  # Make typing an optional import to avoid it being a required dependency
  # in Python 2. Type checkers will still understand the imports.
  try:
    # pylint: disable=unused-import
    import typing
    from typing import Any, AnyStr, BinaryIO, Callable, ContextManager, IO, Iterator, List, Mapping, MutableMapping, MutableSequence, Optional, Sequence, Text, TextIO, Tuple, Type, Union
    # pylint: enable=unused-import
  except ImportError:
    pass
  else:
    # Use an if-type-checking block to prevent leakage of type-checking only
    # symbols. We don't want people relying on these at runtime.
    if typing.TYPE_CHECKING:
      # Unbounded TypeVar for general usage
      _T = typing.TypeVar('_T')
  
      if six.PY2:
        _OutcomeType = unittest3_backport.case._Outcome
      else:
        import unittest.case
        _OutcomeType = unittest.case._Outcome  # pytype: disable=module-attr
  
  
  if six.PY3:
    from unittest import mock  # pylint: disable=unused-import
  else:
    try:
      import mock  # type: ignore
    except ImportError:
      mock = None
  
  
  # Re-export a bunch of unittest functions we support so that people don't
  # have to import unittest to get them
  # pylint: disable=invalid-name
  skip = unittest.skip
  skipIf = unittest.skipIf
  skipUnless = unittest.skipUnless
  SkipTest = unittest.SkipTest
  expectedFailure = unittest.expectedFailure
  # pylint: enable=invalid-name
  
  # End unittest re-exports
  
  FLAGS = flags.FLAGS
  
  _TEXT_OR_BINARY_TYPES = (six.text_type, six.binary_type)
  
  
  def expectedFailureIf(condition, reason):  # pylint: disable=invalid-name
    """Expects the test to fail if the run condition is True.
  
    Example usage:
      @expectedFailureIf(sys.version.major == 2, "Not yet working in py2")
      def test_foo(self):
        ...
  
    Args:
      condition: bool, whether to expect failure or not.
      reason: Text, the reason to expect failure.
    Returns:
      Decorator function
    """
    del reason  # Unused
    if condition:
      return unittest.expectedFailure
    else:
      return lambda f: f
  
  
  class TempFileCleanup(enum.Enum):
    # Always cleanup temp files when the test completes.
    ALWAYS = 'always'
    # Only cleanup temp file if the test passes. This allows easier inspection
    # of tempfile contents on test failure. FLAGS.test_tempdir determines
    # where tempfiles are created.
    SUCCESS = 'success'
    # Never cleanup temp files.
    OFF = 'never'
  
  
  # Many of the methods in this module have names like assertSameElements.
  # This kind of name does not comply with PEP8 style,
  # but it is consistent with the naming of methods in unittest.py.
  # pylint: disable=invalid-name
  
  
  def _get_default_test_random_seed():
    # type: () -> int
    random_seed = 301
    value = os.environ.get('TEST_RANDOM_SEED', '')
    try:
      random_seed = int(value)
    except ValueError:
      pass
    return random_seed
  
  
  def get_default_test_srcdir():
    # type: () -> Text
    """Returns default test source dir."""
    return os.environ.get('TEST_SRCDIR', '')
  
  
  def get_default_test_tmpdir():
    # type: () -> Text
    """Returns default test temp dir."""
    tmpdir = os.environ.get('TEST_TMPDIR', '')
    if not tmpdir:
      tmpdir = os.path.join(tempfile.gettempdir(), 'absl_testing')
  
    return tmpdir
  
  
  def _get_default_randomize_ordering_seed():
    # type: () -> int
    """Returns default seed to use for randomizing test order.
  
    This function first checks the --test_randomize_ordering_seed flag, and then
    the TEST_RANDOMIZE_ORDERING_SEED environment variable. If the first value
    we find is:
      * (not set): disable test randomization
      * 0: disable test randomization
      * 'random': choose a random seed in [1, 4294967295] for test order
        randomization
      * positive integer: use this seed for test order randomization
  
    (The values used are patterned after
    https://docs.python.org/3/using/cmdline.html#envvar-PYTHONHASHSEED).
  
    In principle, it would be simpler to return None if no override is provided;
    however, the python random module has no `get_seed()`, only `getstate()`,
    which returns far more data than we want to pass via an environment variable
    or flag.
  
    Returns:
      A default value for test case randomization (int). 0 means do not randomize.
  
    Raises:
      ValueError: Raised when the flag or env value is not one of the options
          above.
    """
    randomize = FLAGS.test_randomize_ordering_seed
    if not randomize:
      return 0
    if randomize == 'random':
      return random.Random().randint(1, 4294967295)
    if randomize == '0':
      return 0
    try:
      seed = int(randomize)
      if seed > 0:
        return seed
    except ValueError:
      pass
    raise ValueError(
        'Unknown test randomization seed value: {}'.format(randomize))
  
  
  flags.DEFINE_integer('test_random_seed', _get_default_test_random_seed(),
                       'Random seed for testing. Some test frameworks may '
                       'change the default value of this flag between runs, so '
                       'it is not appropriate for seeding probabilistic tests.',
                       allow_override_cpp=True)
  flags.DEFINE_string('test_srcdir',
                      get_default_test_srcdir(),
                      'Root of directory tree where source files live',
                      allow_override_cpp=True)
  flags.DEFINE_string('test_tmpdir', get_default_test_tmpdir(),
                      'Directory for temporary testing files',
                      allow_override_cpp=True)
  flags.DEFINE_string('test_randomize_ordering_seed',
                      os.environ.get('TEST_RANDOMIZE_ORDERING_SEED', ''),
                      'If positive, use this as a seed to randomize the '
                      'execution order for test cases. If "random", pick a '
                      'random seed to use. If 0 or not set, do not randomize '
                      'test case execution order. This flag also overrides '
                      'the TEST_RANDOMIZE_ORDERING_SEED environment variable.',
                      allow_override_cpp=True)
  flags.DEFINE_string('xml_output_file', '',
                      'File to store XML test results')
  
  
  # We might need to monkey-patch TestResult so that it stops considering an
  # unexpected pass as a as a "successful result".  For details, see
  # http://bugs.python.org/issue20165
  def _monkey_patch_test_result_for_unexpected_passes():
    # type: () -> None
    """Workaround for <http://bugs.python.org/issue20165>."""
  
    def wasSuccessful(self):
      # type: (unittest.TestResult) -> bool
      """Tells whether or not this result was a success.
  
      Any unexpected pass is to be counted as a non-success.
  
      Args:
        self: The TestResult instance.
  
      Returns:
        Whether or not this result was a success.
      """
      return (len(self.failures) == len(self.errors) ==
              len(self.unexpectedSuccesses) == 0)
  
    test_result = unittest.TestResult()
    test_result.addUnexpectedSuccess(unittest.FunctionTestCase(lambda: None))
    if test_result.wasSuccessful():  # The bug is present.
      unittest.TestResult.wasSuccessful = wasSuccessful
      if test_result.wasSuccessful():  # Warn the user if our hot-fix failed.
        sys.stderr.write('unittest.result.TestResult monkey patch to report'
                         ' unexpected passes as failures did not work.\n')
  
  
  _monkey_patch_test_result_for_unexpected_passes()
  
  
  def _open(filepath, mode, _open_func=open):
    # type: (Text, Text, Callable[..., IO]) -> IO
    """Opens a file.
  
    Like open(), but compatible with Python 2 and 3. Also ensures that we can open
    real files even if tests stub out open().
  
    Args:
      filepath: A filepath.
      mode: A mode.
      _open_func: A built-in open() function.
  
    Returns:
      The opened file object.
    """
    if six.PY2:
      return _open_func(filepath, mode)
    else:
      return _open_func(filepath, mode, encoding='utf-8')
  
  
  class _TempDir(object):
    """Represents a temporary directory for tests.
  
    Creation of this class is internal. Using its public methods is OK.
    """
  
    def __init__(self, path):
      # type: (Text) -> None
      """Module-private: do not instantiate outside module."""
      self._path = path
  
    @property
    def full_path(self):
      # type: () -> Text
      """The path, as a string, for the directory."""
      return self._path
  
    def create_file(self, file_path=None, content=None, mode='w', encoding='utf8',
                    errors='strict'):
      # type: (Optional[Text], Optional[AnyStr], Text, Text, Text) -> _TempFile
      """Create a file in the directory.
  
      NOTE: If the file already exists, it will be made writable and overwritten.
  
      Args:
        file_path: Optional file path for the temp file. If not given, a unique
          file name will be generated and used. Slashes are allowed in the name;
          any missing intermediate directories will be created. NOTE: This path
          is the path that will be cleaned up, including any directories in the
          path, e.g., 'foo/bar/baz.txt' will `rm -r foo`
        content: Optional string or bytes to initially write to the file. If not
          specified, then an empty file is created.
        mode: Mode string to use when writing content. Only used if `content` is
          non-empty.
        encoding: Encoding to use when writing string content. Only used if
          `content` is text.
        errors: How to handle text to bytes encoding errors. Only used if
          `content` is text.
  
      Returns:
        A _TempFile representing the created file.
      """
      tf, _ = _TempFile._create(self._path, file_path, content, mode, encoding,
                                errors)
      return tf
  
    def mkdir(self, dir_path=None):
      # type: (Optional[Text]) -> _TempDir
      """Create a directory in the directory.
  
      Args:
        dir_path: Optional path to the directory to create. If not given,
          a unique name will be generated and used.
  
      Returns:
        A _TempDir representing the created directory.
      """
      if dir_path:
        path = os.path.join(self._path, dir_path)
      else:
        path = tempfile.mkdtemp(dir=self._path)
  
      # Note: there's no need to clear the directory since the containing
      # dir was cleared by the tempdir() function.
      _makedirs_exist_ok(path)
      return _TempDir(path)
  
  
  class _TempFile(object):
    """Represents a tempfile for tests.
  
    Creation of this class is internal. Using its public methods is OK.
    """
  
    def __init__(self, path):
      # type: (Text) -> None
      """Private: use _create instead."""
      self._path = path
  
    # pylint: disable=line-too-long
    @classmethod
    def _create(cls, base_path, file_path, content, mode, encoding, errors):
      # type: (Text, Optional[Text], Optional[AnyStr], Text, Text, Text) -> Tuple[_TempFile, Text]
      # pylint: enable=line-too-long
      """Module-private: create a tempfile instance."""
      if file_path:
        cleanup_path = os.path.join(base_path, _get_first_part(file_path))
        path = os.path.join(base_path, file_path)
        _makedirs_exist_ok(os.path.dirname(path))
        # The file may already exist, in which case, ensure it's writable so that
        # it can be truncated.
        if os.path.exists(path) and not os.access(path, os.W_OK):
          stat_info = os.stat(path)
          os.chmod(path, stat_info.st_mode | stat.S_IWUSR)
      else:
        _makedirs_exist_ok(base_path)
        fd, path = tempfile.mkstemp(dir=str(base_path))
        os.close(fd)
        cleanup_path = path
  
      tf = cls(path)
  
      if content:
        if isinstance(content, six.text_type):
          tf.write_text(content, mode=mode, encoding=encoding, errors=errors)
        else:
          tf.write_bytes(content, mode)
  
      else:
        tf.write_bytes(b'')
  
      return tf, cleanup_path
  
    @property
    def full_path(self):
      # type: () -> Text
      """The path, as a string, for the file."""
      return self._path
  
    def read_text(self, encoding='utf8', errors='strict'):
      # type: (Text, Text) -> Text
      """Return the contents of the file as text."""
      with self.open_text(encoding=encoding, errors=errors) as fp:
        return fp.read()
  
    def read_bytes(self):
      # type: () -> bytes
      """Return the content of the file as bytes."""
      with self.open_bytes() as fp:
        return fp.read()
  
    def write_text(self, text, mode='w', encoding='utf8', errors='strict'):
      # type: (Text, Text, Text, Text) -> None
      """Write text to the file.
  
      Args:
        text: Text to write. In Python 2, it can be bytes, which will be
          decoded using the `encoding` arg (this is as an aid for code that
          is 2 and 3 compatible).
        mode: The mode to open the file for writing.
        encoding: The encoding to use when writing the text to the file.
        errors: The error handling strategy to use when converting text to bytes.
      """
      if six.PY2 and isinstance(text, bytes):
        text = text.decode(encoding, errors)
      with self.open_text(mode, encoding=encoding, errors=errors) as fp:
        fp.write(text)
  
    def write_bytes(self, data, mode='wb'):
      # type: (bytes, Text) -> None
      """Write bytes to the file.
  
      Args:
        data: bytes to write.
        mode: Mode to open the file for writing. The "b" flag is implicit if
          not already present. It must not have the "t" flag.
      """
      with self.open_bytes(mode) as fp:
        fp.write(data)
  
    def open_text(self, mode='rt', encoding='utf8', errors='strict'):
      # type: (Text, Text, Text) -> ContextManager[TextIO]
      """Return a context manager for opening the file in text mode.
  
      Args:
        mode: The mode to open the file in. The "t" flag is implicit if not
          already present. It must not have the "b" flag.
        encoding: The encoding to use when opening the file.
        errors: How to handle decoding errors.
  
      Returns:
        Context manager that yields an open file.
  
      Raises:
        ValueError: if invalid inputs are provided.
      """
      if 'b' in mode:
        raise ValueError('Invalid mode {!r}: "b" flag not allowed when opening '
                         'file in text mode'.format(mode))
      if 't' not in mode:
        mode += 't'
      cm = self._open(mode, encoding, errors)  # type: ContextManager[TextIO]
      return cm
  
    def open_bytes(self, mode='rb'):
      # type: (Text) -> ContextManager[BinaryIO]
      """Return a context manager for opening the file in binary mode.
  
      Args:
        mode: The mode to open the file in. The "b" mode is implicit if not
          already present. It must not have the "t" flag.
  
      Returns:
        Context manager that yields an open file.
  
      Raises:
        ValueError: if invalid inputs are provided.
      """
      if 't' in mode:
        raise ValueError('Invalid mode {!r}: "t" flag not allowed when opening '
                         'file in binary mode'.format(mode))
      if 'b' not in mode:
        mode += 'b'
      cm = self._open(mode, encoding=None, errors=None)  # type: ContextManager[BinaryIO]
      return cm
  
    # TODO(b/123775699): Once pytype supports typing.Literal, use overload and
    # Literal to express more precise return types and remove the type comments in
    # open_text and open_bytes.
    @contextlib.contextmanager
    def _open(self, mode, encoding='utf8', errors='strict'):
      # type: (Text, Optional[Text], Optional[Text]) -> Iterator[Union[IO[Text], IO[bytes]]]
      with io.open(
          self.full_path, mode=mode, encoding=encoding, errors=errors) as fp:
        yield fp
  
  
  class TestCase(unittest3_backport.TestCase):
    """Extension of unittest.TestCase providing more power."""
  
    # When to cleanup files/directories created by our `create_tempfile()` and
    # `create_tempdir()` methods after each test case completes. This does *not*
    # affect e.g., files created outside of those methods, e.g., using the stdlib
    # tempfile module. This can be overridden at the class level, instance level,
    # or with the `cleanup` arg of `create_tempfile()` and `create_tempdir()`. See
    # `TempFileCleanup` for details on the different values.
    tempfile_cleanup = TempFileCleanup.ALWAYS  # type: TempFileCleanup
  
    maxDiff = 80 * 20
    longMessage = True
  
    def __init__(self, *args, **kwargs):
      super(TestCase, self).__init__(*args, **kwargs)
      # This is to work around missing type stubs in unittest.pyi
      self._outcome = getattr(self, '_outcome')  # type: Optional[_OutcomeType]
      # This is re-initialized by setUp().
      self._exit_stack = None
  
    def setUp(self):
      super(TestCase, self).setUp()
      # NOTE: Only Py3 contextlib has ExitStack
      if hasattr(contextlib, 'ExitStack'):
        self._exit_stack = contextlib.ExitStack()
        self.addCleanup(self._exit_stack.close)
  
    def create_tempdir(self, name=None, cleanup=None):
      # type: (Optional[Text], Optional[TempFileCleanup]) -> _TempDir
      """Create a temporary directory specific to the test.
  
      NOTE: The directory and its contents will be recursively cleared before
      creation. This ensures that there is no pre-existing state.
  
      This creates a named directory on disk that is isolated to this test, and
      will be properly cleaned up by the test. This avoids several pitfalls of
      creating temporary directories for test purposes, as well as makes it easier
      to setup directories and verify their contents.
  
      See also: `create_tempfile()` for creating temporary files.
  
      Args:
        name: Optional name of the directory. If not given, a unique
          name will be generated and used.
        cleanup: Optional cleanup policy on when/if to remove the directory (and
          all its contents) at the end of the test. If None, then uses
          `self.tempfile_cleanup`.
  
      Returns:
        A _TempDir representing the created directory.
      """
      test_path = self._get_tempdir_path_test()
  
      if name:
        path = os.path.join(test_path, name)
        cleanup_path = os.path.join(test_path, _get_first_part(name))
      else:
        _makedirs_exist_ok(test_path)
        path = tempfile.mkdtemp(dir=test_path)
        cleanup_path = path
  
      _rmtree_ignore_errors(cleanup_path)
      _makedirs_exist_ok(path)
  
      self._maybe_add_temp_path_cleanup(cleanup_path, cleanup)
  
      return _TempDir(path)
  
    # pylint: disable=line-too-long
    def create_tempfile(self, file_path=None, content=None, mode='w',
                        encoding='utf8', errors='strict', cleanup=None):
      # type: (Optional[Text], Optional[AnyStr], Text, Text, Text, Optional[TempFileCleanup]) -> _TempFile
      # pylint: enable=line-too-long
      """Create a temporary file specific to the test.
  
      This creates a named file on disk that is isolated to this test, and will
      be properly cleaned up by the test. This avoids several pitfalls of
      creating temporary files for test purposes, as well as makes it easier
      to setup files, their data, read them back, and inspect them when
      a test fails.
  
      NOTE: This will zero-out the file. This ensures there is no pre-existing
      state.
      NOTE: If the file already exists, it will be made writable and overwritten.
  
      See also: `create_tempdir()` for creating temporary directories, and
      `_TempDir.create_file` for creating files within a temporary directory.
  
      Args:
        file_path: Optional file path for the temp file. If not given, a unique
          file name will be generated and used. Slashes are allowed in the name;
          any missing intermediate directories will be created. NOTE: This path is
          the path that will be cleaned up, including any directories in the path,
          e.g., 'foo/bar/baz.txt' will `rm -r foo`.
        content: Optional string or
          bytes to initially write to the file. If not
          specified, then an empty file is created.
        mode: Mode string to use when writing content. Only used if `content` is
          non-empty.
        encoding: Encoding to use when writing string content. Only used if
          `content` is text.
        errors: How to handle text to bytes encoding errors. Only used if
          `content` is text.
        cleanup: Optional cleanup policy on when/if to remove the directory (and
          all its contents) at the end of the test. If None, then uses
          `self.tempfile_cleanup`.
  
      Returns:
        A _TempFile representing the created file.
      """
      test_path = self._get_tempdir_path_test()
      tf, cleanup_path = _TempFile._create(test_path, file_path, content=content,
                                           mode=mode, encoding=encoding,
                                           errors=errors)
      self._maybe_add_temp_path_cleanup(cleanup_path, cleanup)
      return tf
  
    def enter_context(self, manager):
      # type: (ContextManager[_T]) -> _T
      """Returns the CM's value after registering it with the exit stack.
  
      Entering a context pushes it onto a stack of contexts. The context is exited
      when the test completes. Contexts are are exited in the reverse order of
      entering. They will always be exited, regardless of test failure/success.
      The context stack is specific to the test being run.
  
      This is useful to eliminate per-test boilerplate when context managers
      are used. For example, instead of decorating every test with `@mock.patch`,
      simply do `self.foo = self.enter_context(mock.patch(...))' in `setUp()`.
  
      NOTE: The context managers will always be exited without any error
      information. This is an unfortunate implementation detail due to some
      internals of how unittest runs tests.
  
      Args:
        manager: The context manager to enter.
      """
      if not self._exit_stack:
        raise AssertionError(
            'self._exit_stack is not set: enter_context is Py3-only; also make '
            'sure that AbslTest.setUp() is called.')
      return self._exit_stack.enter_context(manager)
  
    @classmethod
    def _get_tempdir_path_cls(cls):
      # type: () -> Text
      return os.path.join(FLAGS.test_tmpdir, _get_qualname(cls))
  
    def _get_tempdir_path_test(self):
      # type: () -> Text
      return os.path.join(self._get_tempdir_path_cls(), self._testMethodName)
  
    def _get_tempfile_cleanup(self, override):
      # type: (Optional[TempFileCleanup]) -> TempFileCleanup
      if override is not None:
        return override
      return self.tempfile_cleanup
  
    def _maybe_add_temp_path_cleanup(self, path, cleanup):
      # type: (Text, Optional[TempFileCleanup]) -> None
      cleanup = self._get_tempfile_cleanup(cleanup)
      if cleanup == TempFileCleanup.OFF:
        return
      elif cleanup == TempFileCleanup.ALWAYS:
        self.addCleanup(_rmtree_ignore_errors, path)
      elif cleanup == TempFileCleanup.SUCCESS:
        self._internal_cleanup_on_success(_rmtree_ignore_errors, path)
      else:
        raise AssertionError('Unexpected cleanup value: {}'.format(cleanup))
  
    def _internal_cleanup_on_success(self, function, *args, **kwargs):
      # type: (Callable[..., object], Any, Any) -> None
      def _call_cleaner_on_success(*args, **kwargs):
        if not self._ran_and_passed():
          return
        function(*args, **kwargs)
      self.addCleanup(_call_cleaner_on_success, *args, **kwargs)
  
    def _ran_and_passed(self):
      # type: () -> bool
      outcome = self._outcome
      result = self.defaultTestResult()
      self._feedErrorsToResult(result, outcome.errors)  # pytype: disable=attribute-error
      return result.wasSuccessful()
  
    def shortDescription(self):
      # type: () -> Text
      """Formats both the test method name and the first line of its docstring.
  
      If no docstring is given, only returns the method name.
  
      This method overrides unittest.TestCase.shortDescription(), which
      only returns the first line of the docstring, obscuring the name
      of the test upon failure.
  
      Returns:
        desc: A short description of a test method.
      """
      desc = str(self)
      # NOTE: super() is used here instead of directly invoking
      # unittest.TestCase.shortDescription(self), because of the
      # following line that occurs later on:
      #       unittest.TestCase = TestCase
      # Because of this, direct invocation of what we think is the
      # superclass will actually cause infinite recursion.
      doc_first_line = super(TestCase, self).shortDescription()
      if doc_first_line is not None:
        desc = '\n'.join((desc, doc_first_line))
      return desc
  
    def assertStartsWith(self, actual, expected_start, msg=None):
      """Asserts that actual.startswith(expected_start) is True.
  
      Args:
        actual: str
        expected_start: str
        msg: Optional message to report on failure.
      """
      if not actual.startswith(expected_start):
        self.fail('%r does not start with %r' % (actual, expected_start), msg)
  
    def assertNotStartsWith(self, actual, unexpected_start, msg=None):
      """Asserts that actual.startswith(unexpected_start) is False.
  
      Args:
        actual: str
        unexpected_start: str
        msg: Optional message to report on failure.
      """
      if actual.startswith(unexpected_start):
        self.fail('%r does start with %r' % (actual, unexpected_start), msg)
  
    def assertEndsWith(self, actual, expected_end, msg=None):
      """Asserts that actual.endswith(expected_end) is True.
  
      Args:
        actual: str
        expected_end: str
        msg: Optional message to report on failure.
      """
      if not actual.endswith(expected_end):
        self.fail('%r does not end with %r' % (actual, expected_end), msg)
  
    def assertNotEndsWith(self, actual, unexpected_end, msg=None):
      """Asserts that actual.endswith(unexpected_end) is False.
  
      Args:
        actual: str
        unexpected_end: str
        msg: Optional message to report on failure.
      """
      if actual.endswith(unexpected_end):
        self.fail('%r does end with %r' % (actual, unexpected_end), msg)
  
    def assertSequenceStartsWith(self, prefix, whole, msg=None):
      """An equality assertion for the beginning of ordered sequences.
  
      If prefix is an empty sequence, it will raise an error unless whole is also
      an empty sequence.
  
      If prefix is not a sequence, it will raise an error if the first element of
      whole does not match.
  
      Args:
        prefix: A sequence expected at the beginning of the whole parameter.
        whole: The sequence in which to look for prefix.
        msg: Optional message to report on failure.
      """
      try:
        prefix_len = len(prefix)
      except (TypeError, NotImplementedError):
        prefix = [prefix]
        prefix_len = 1
  
      try:
        whole_len = len(whole)
      except (TypeError, NotImplementedError):
        self.fail('For whole: len(%s) is not supported, it appears to be type: '
                  '%s' % (whole, type(whole)), msg)
  
      assert prefix_len <= whole_len, self._formatMessage(
          msg,
          'Prefix length (%d) is longer than whole length (%d).' %
          (prefix_len, whole_len)
      )
  
      if not prefix_len and whole_len:
        self.fail('Prefix length is 0 but whole length is %d: %s' %
                  (len(whole), whole), msg)
  
      try:
        self.assertSequenceEqual(prefix, whole[:prefix_len], msg)
      except AssertionError:
        self.fail('prefix: %s not found at start of whole: %s.' %
                  (prefix, whole), msg)
  
    def assertEmpty(self, container, msg=None):
      """Asserts that an object has zero length.
  
      Args:
        container: Anything that implements the collections.abc.Sized interface.
        msg: Optional message to report on failure.
      """
      if not isinstance(container, abc.Sized):
        self.fail('Expected a Sized object, got: '
                  '{!r}'.format(type(container).__name__), msg)
  
      # explicitly check the length since some Sized objects (e.g. numpy.ndarray)
      # have strange __nonzero__/__bool__ behavior.
      if len(container):  # pylint: disable=g-explicit-length-test
        self.fail('{!r} has length of {}.'.format(container, len(container)), msg)
  
    def assertNotEmpty(self, container, msg=None):
      """Asserts that an object has non-zero length.
  
      Args:
        container: Anything that implements the collections.abc.Sized interface.
        msg: Optional message to report on failure.
      """
      if not isinstance(container, abc.Sized):
        self.fail('Expected a Sized object, got: '
                  '{!r}'.format(type(container).__name__), msg)
  
      # explicitly check the length since some Sized objects (e.g. numpy.ndarray)
      # have strange __nonzero__/__bool__ behavior.
      if not len(container):  # pylint: disable=g-explicit-length-test
        self.fail('{!r} has length of 0.'.format(container), msg)
  
    def assertLen(self, container, expected_len, msg=None):
      """Asserts that an object has the expected length.
  
      Args:
        container: Anything that implements the collections.abc.Sized interface.
        expected_len: The expected length of the container.
        msg: Optional message to report on failure.
      """
      if not isinstance(container, abc.Sized):
        self.fail('Expected a Sized object, got: '
                  '{!r}'.format(type(container).__name__), msg)
      if len(container) != expected_len:
        container_repr = unittest.util.safe_repr(container)  # pytype: disable=module-attr
        self.fail('{} has length of {}, expected {}.'.format(
            container_repr, len(container), expected_len), msg)
  
    def assertSequenceAlmostEqual(self, expected_seq, actual_seq, places=None,
                                  msg=None, delta=None):
      """An approximate equality assertion for ordered sequences.
  
      Fail if the two sequences are unequal as determined by their value
      differences rounded to the given number of decimal places (default 7) and
      comparing to zero, or by comparing that the difference between each value
      in the two sequences is more than the given delta.
  
      Note that decimal places (from zero) are usually not the same as significant
      digits (measured from the most significant digit).
  
      If the two sequences compare equal then they will automatically compare
      almost equal.
  
      Args:
        expected_seq: A sequence containing elements we are expecting.
        actual_seq: The sequence that we are testing.
        places: The number of decimal places to compare.
        msg: The message to be printed if the test fails.
        delta: The OK difference between compared values.
      """
      if len(expected_seq) != len(actual_seq):
        self.fail('Sequence size mismatch: {} vs {}'.format(
            len(expected_seq), len(actual_seq)), msg)
  
      err_list = []
      for idx, (exp_elem, act_elem) in enumerate(zip(expected_seq, actual_seq)):
        try:
          # assertAlmostEqual should be called with at most one of `places` and
          # `delta`. However, it's okay for assertSequenceAlmostEqual to pass
          # both because we want the latter to fail if the former does.
          # pytype: disable=wrong-keyword-args
          self.assertAlmostEqual(exp_elem, act_elem, places=places, msg=msg,
                                 delta=delta)
          # pytype: enable=wrong-keyword-args
        except self.failureException as err:
          err_list.append('At index {}: {}'.format(idx, err))
  
      if err_list:
        if len(err_list) > 30:
          err_list = err_list[:30] + ['...']
        msg = self._formatMessage(msg, '\n'.join(err_list))
        self.fail(msg)
  
    def assertContainsSubset(self, expected_subset, actual_set, msg=None):
      """Checks whether actual iterable is a superset of expected iterable."""
      missing = set(expected_subset) - set(actual_set)
      if not missing:
        return
  
      self.fail('Missing elements %s\nExpected: %s\nActual: %s' % (
          missing, expected_subset, actual_set), msg)
  
    def assertNoCommonElements(self, expected_seq, actual_seq, msg=None):
      """Checks whether actual iterable and expected iterable are disjoint."""
      common = set(expected_seq) & set(actual_seq)
      if not common:
        return
  
      self.fail('Common elements %s\nExpected: %s\nActual: %s' % (
          common, expected_seq, actual_seq), msg)
  
    def assertItemsEqual(self, expected_seq, actual_seq, msg=None):
      """Deprecated, please use assertCountEqual instead.
  
      This is equivalent to assertCountEqual in Python 3. An implementation of
      assertCountEqual is also provided by absltest.TestCase for Python 2.
  
      Args:
        expected_seq: A sequence containing elements we are expecting.
        actual_seq: The sequence that we are testing.
        msg: The message to be printed if the test fails.
      """
      if six.PY3:
        # The assertItemsEqual method was renamed assertCountEqual in Python 3.2
        super(TestCase, self).assertCountEqual(expected_seq, actual_seq, msg)
      else:
        super(TestCase, self).assertItemsEqual(expected_seq, actual_seq, msg)
  
    # Only override assertCountEqual in Python 2 to avoid unnecessary calls.
    if six.PY2:
  
      def assertCountEqual(self, expected_seq, actual_seq, msg=None):
        """Tests two sequences have the same elements regardless of order.
  
        It tests that the first sequence contains the same elements as the
        second, regardless of their order. When they don't, an error message
        listing the differences between the sequences will be generated.
  
        Duplicate elements are not ignored when comparing first and second.
        It verifies whether each element has the same count in both sequences.
        Equivalent to:
  
            self.assertEqual(Counter(list(expected_seq)),
                             Counter(list(actual_seq)))
  
        but works with sequences of unhashable objects as well.
  
        Example:
            - [0, 1, 1] and [1, 0, 1] compare equal.
            - [0, 0, 1] and [0, 1] compare unequal.
  
        Args:
          expected_seq: A sequence containing elements we are expecting.
          actual_seq: The sequence that we are testing.
          msg: The message to be printed if the test fails.
  
        """
        # Only call super's method to avoid potential infinite recursions.
        super(TestCase, self).assertItemsEqual(expected_seq, actual_seq, msg)
  
    def assertSameElements(self, expected_seq, actual_seq, msg=None):
      """Asserts that two sequences have the same elements (in any order).
  
      This method, unlike assertCountEqual, doesn't care about any
      duplicates in the expected and actual sequences.
  
        >> assertSameElements([1, 1, 1, 0, 0, 0], [0, 1])
        # Doesn't raise an AssertionError
  
      If possible, you should use assertCountEqual instead of
      assertSameElements.
  
      Args:
        expected_seq: A sequence containing elements we are expecting.
        actual_seq: The sequence that we are testing.
        msg: The message to be printed if the test fails.
      """
      # `unittest2.TestCase` used to have assertSameElements, but it was
      # removed in favor of assertItemsEqual. As there's a unit test
      # that explicitly checks this behavior, I am leaving this method
      # alone.
      # Fail on strings: empirically, passing strings to this test method
      # is almost always a bug. If comparing the character sets of two strings
      # is desired, cast the inputs to sets or lists explicitly.
      if (isinstance(expected_seq, _TEXT_OR_BINARY_TYPES) or
          isinstance(actual_seq, _TEXT_OR_BINARY_TYPES)):
        self.fail('Passing string/bytes to assertSameElements is usually a bug. '
                  'Did you mean to use assertEqual?\n'
                  'Expected: %s\nActual: %s' % (expected_seq, actual_seq))
      try:
        expected = dict([(element, None) for element in expected_seq])
        actual = dict([(element, None) for element in actual_seq])
        missing = [element for element in expected if element not in actual]
        unexpected = [element for element in actual if element not in expected]
        missing.sort()
        unexpected.sort()
      except TypeError:
        # Fall back to slower list-compare if any of the objects are
        # not hashable.
        expected = list(expected_seq)
        actual = list(actual_seq)
        expected.sort()
        actual.sort()
        missing, unexpected = _sorted_list_difference(expected, actual)
      errors = []
      if msg:
        errors.extend((msg, ':\n'))
      if missing:
        errors.append('Expected, but missing:\n  %r\n' % missing)
      if unexpected:
        errors.append('Unexpected, but present:\n  %r\n' % unexpected)
      if missing or unexpected:
        self.fail(''.join(errors))
  
    # unittest.TestCase.assertMultiLineEqual works very similarly, but it
    # has a different error format. However, I find this slightly more readable.
    def assertMultiLineEqual(self, first, second, msg=None, **kwargs):
      """Asserts that two multi-line strings are equal."""
      assert isinstance(first, six.string_types), (
          'First argument is not a string: %r' % (first,))
      assert isinstance(second, six.string_types), (
          'Second argument is not a string: %r' % (second,))
      line_limit = kwargs.pop('line_limit', 0)
      if kwargs:
        raise TypeError('Unexpected keyword args {}'.format(tuple(kwargs)))
  
      if first == second:
        return
      if msg:
        failure_message = [msg + ':\n']
      else:
        failure_message = ['\n']
      if line_limit:
        line_limit += len(failure_message)
      for line in difflib.ndiff(first.splitlines(True), second.splitlines(True)):
        failure_message.append(line)
        if not line.endswith('\n'):
          failure_message.append('\n')
      if line_limit and len(failure_message) > line_limit:
        n_omitted = len(failure_message) - line_limit
        failure_message = failure_message[:line_limit]
        failure_message.append(
            '(... and {} more delta lines omitted for brevity.)\n'.format(
                n_omitted))
  
      raise self.failureException(''.join(failure_message))
  
    def assertBetween(self, value, minv, maxv, msg=None):
      """Asserts that value is between minv and maxv (inclusive)."""
      msg = self._formatMessage(msg,
                                '"%r" unexpectedly not between "%r" and "%r"' %
                                (value, minv, maxv))
      self.assertTrue(minv <= value, msg)
      self.assertTrue(maxv >= value, msg)
  
    # Backport these names so that Py2 code can be written in Py3 style.
    if six.PY2:
  
      def assertRegex(self, *args, **kwargs):
        return self.assertRegexpMatches(*args, **kwargs)
  
      def assertRaisesRegex(self, *args, **kwargs):
        return self.assertRaisesRegexp(*args, **kwargs)
  
      def assertNotRegex(self, *args, **kwargs):
        return self.assertNotRegexpMatches(*args, **kwargs)
  
    def assertRegexMatch(self, actual_str, regexes, message=None):
      r"""Asserts that at least one regex in regexes matches str.
  
      If possible you should use `assertRegex`, which is a simpler
      version of this method. `assertRegex` takes a single regular
      expression (a string or re compiled object) instead of a list.
  
      Notes:
      1. This function uses substring matching, i.e. the matching
         succeeds if *any* substring of the error message matches *any*
         regex in the list.  This is more convenient for the user than
         full-string matching.
  
      2. If regexes is the empty list, the matching will always fail.
  
      3. Use regexes=[''] for a regex that will always pass.
  
      4. '.' matches any single character *except* the newline.  To
         match any character, use '(.|\n)'.
  
      5. '^' matches the beginning of each line, not just the beginning
         of the string.  Similarly, '$' matches the end of each line.
  
      6. An exception will be thrown if regexes contains an invalid
         regex.
  
      Args:
        actual_str:  The string we try to match with the items in regexes.
        regexes:  The regular expressions we want to match against str.
            See "Notes" above for detailed notes on how this is interpreted.
        message:  The message to be printed if the test fails.
      """
      if isinstance(regexes, _TEXT_OR_BINARY_TYPES):
        self.fail('regexes is string or bytes; use assertRegex instead.',
                  message)
      if not regexes:
        self.fail('No regexes specified.', message)
  
      regex_type = type(regexes[0])
      for regex in regexes[1:]:
        if type(regex) is not regex_type:  # pylint: disable=unidiomatic-typecheck
          self.fail('regexes list must all be the same type.', message)
  
      if regex_type is bytes and isinstance(actual_str, six.text_type):
        regexes = [regex.decode('utf-8') for regex in regexes]
        regex_type = six.text_type
      elif regex_type is six.text_type and isinstance(actual_str, bytes):
        regexes = [regex.encode('utf-8') for regex in regexes]
        regex_type = bytes
  
      if regex_type is six.text_type:
        regex = u'(?:%s)' % u')|(?:'.join(regexes)
      elif regex_type is bytes:
        regex = b'(?:' + (b')|(?:'.join(regexes)) + b')'
      else:
        self.fail('Only know how to deal with unicode str or bytes regexes.',
                  message)
  
      if not re.search(regex, actual_str, re.MULTILINE):
        self.fail('"%s" does not contain any of these regexes: %s.' %
                  (actual_str, regexes), message)
  
    def assertCommandSucceeds(self, command, regexes=(b'',), env=None,
                              close_fds=True, msg=None):
      """Asserts that a shell command succeeds (i.e. exits with code 0).
  
      Args:
        command: List or string representing the command to run.
        regexes: List of regular expression byte strings that match success.
        env: Dictionary of environment variable settings. If None, no environment
            variables will be set for the child process. This is to make tests
            more hermetic. NOTE: this behavior is different than the standard
            subprocess module.
        close_fds: Whether or not to close all open fd's in the child after
            forking.
        msg: Optional message to report on failure.
      """
      (ret_code, err) = get_command_stderr(command, env, close_fds)
  
      # We need bytes regexes here because `err` is bytes.
      # Accommodate code which listed their output regexes w/o the b'' prefix by
      # converting them to bytes for the user.
      if isinstance(regexes[0], six.text_type):
        regexes = [regex.encode('utf-8') for regex in regexes]
  
      command_string = get_command_string(command)
      self.assertEqual(
          ret_code, 0,
          self._formatMessage(msg,
                              'Running command\n'
                              '%s failed with error code %s and message\n'
                              '%s' % (_quote_long_string(command_string),
                                      ret_code,
                                      _quote_long_string(err)))
      )
      self.assertRegexMatch(
          err,
          regexes,
          message=self._formatMessage(
              msg,
              'Running command\n'
              '%s failed with error code %s and message\n'
              '%s which matches no regex in %s' % (
                  _quote_long_string(command_string),
                  ret_code,
                  _quote_long_string(err),
                  regexes)))
  
    def assertCommandFails(self, command, regexes, env=None, close_fds=True,
                           msg=None):
      """Asserts a shell command fails and the error matches a regex in a list.
  
      Args:
        command: List or string representing the command to run.
        regexes: the list of regular expression strings.
        env: Dictionary of environment variable settings. If None, no environment
            variables will be set for the child process. This is to make tests
            more hermetic. NOTE: this behavior is different than the standard
            subprocess module.
        close_fds: Whether or not to close all open fd's in the child after
            forking.
        msg: Optional message to report on failure.
      """
      (ret_code, err) = get_command_stderr(command, env, close_fds)
  
      # We need bytes regexes here because `err` is bytes.
      # Accommodate code which listed their output regexes w/o the b'' prefix by
      # converting them to bytes for the user.
      if isinstance(regexes[0], six.text_type):
        regexes = [regex.encode('utf-8') for regex in regexes]
  
      command_string = get_command_string(command)
      self.assertNotEqual(
          ret_code, 0,
          self._formatMessage(msg, 'The following command succeeded '
                              'while expected to fail:\n%s' %
                              _quote_long_string(command_string)))
      self.assertRegexMatch(
          err,
          regexes,
          message=self._formatMessage(
              msg,
              'Running command\n'
              '%s failed with error code %s and message\n'
              '%s which matches no regex in %s' % (
                  _quote_long_string(command_string),
                  ret_code,
                  _quote_long_string(err),
                  regexes)))
  
    class _AssertRaisesContext(object):
  
      def __init__(self, expected_exception, test_case, test_func, msg=None):
        self.expected_exception = expected_exception
        self.test_case = test_case
        self.test_func = test_func
        self.msg = msg
  
      def __enter__(self):
        return self
  
      def __exit__(self, exc_type, exc_value, tb):
        if exc_type is None:
          self.test_case.fail(self.expected_exception.__name__ + ' not raised',
                              self.msg)
        if not issubclass(exc_type, self.expected_exception):
          return False
        self.test_func(exc_value)
        return True
  
    def assertRaisesWithPredicateMatch(self, expected_exception, predicate,
                                       callable_obj=None, *args, **kwargs):
      """Asserts that exception is thrown and predicate(exception) is true.
  
      Args:
        expected_exception: Exception class expected to be raised.
        predicate: Function of one argument that inspects the passed-in exception
            and returns True (success) or False (please fail the test).
        callable_obj: Function to be called.
        *args: Extra args.
        **kwargs: Extra keyword args.
  
      Returns:
        A context manager if callable_obj is None. Otherwise, None.
  
      Raises:
        self.failureException if callable_obj does not raise a matching exception.
      """
      def Check(err):
        self.assertTrue(predicate(err),
                        '%r does not match predicate %r' % (err, predicate))
  
      context = self._AssertRaisesContext(expected_exception, self, Check)
      if callable_obj is None:
        return context
      with context:
        callable_obj(*args, **kwargs)
  
    def assertRaisesWithLiteralMatch(self, expected_exception,
                                     expected_exception_message,
                                     callable_obj=None, *args, **kwargs):
      """Asserts that the message in a raised exception equals the given string.
  
      Unlike assertRaisesRegex, this method takes a literal string, not
      a regular expression.
  
      with self.assertRaisesWithLiteralMatch(ExType, 'message'):
        DoSomething()
  
      Args:
        expected_exception: Exception class expected to be raised.
        expected_exception_message: String message expected in the raised
            exception.  For a raise exception e, expected_exception_message must
            equal str(e).
        callable_obj: Function to be called, or None to return a context.
        *args: Extra args.
        **kwargs: Extra kwargs.
  
      Returns:
        A context manager if callable_obj is None. Otherwise, None.
  
      Raises:
        self.failureException if callable_obj does not raise a matching exception.
      """
      def Check(err):
        actual_exception_message = str(err)
        self.assertTrue(expected_exception_message == actual_exception_message,
                        'Exception message does not match.\n'
                        'Expected: %r\n'
                        'Actual: %r' % (expected_exception_message,
                                        actual_exception_message))
  
      context = self._AssertRaisesContext(expected_exception, self, Check)
      if callable_obj is None:
        return context
      with context:
        callable_obj(*args, **kwargs)
  
    def assertContainsInOrder(self, strings, target, msg=None):
      """Asserts that the strings provided are found in the target in order.
  
      This may be useful for checking HTML output.
  
      Args:
        strings: A list of strings, such as [ 'fox', 'dog' ]
        target: A target string in which to look for the strings, such as
            'The quick brown fox jumped over the lazy dog'.
        msg: Optional message to report on failure.
      """
      if isinstance(strings, (bytes, unicode if str is bytes else str)):
        strings = (strings,)
  
      current_index = 0
      last_string = None
      for string in strings:
        index = target.find(str(string), current_index)
        if index == -1 and current_index == 0:
          self.fail("Did not find '%s' in '%s'" %
                    (string, target), msg)
        elif index == -1:
          self.fail("Did not find '%s' after '%s' in '%s'" %
                    (string, last_string, target), msg)
        last_string = string
        current_index = index
  
    def assertContainsSubsequence(self, container, subsequence, msg=None):
      """Asserts that "container" contains "subsequence" as a subsequence.
  
      Asserts that "container" contains all the elements of "subsequence", in
      order, but possibly with other elements interspersed. For example, [1, 2, 3]
      is a subsequence of [0, 0, 1, 2, 0, 3, 0] but not of [0, 0, 1, 3, 0, 2, 0].
  
      Args:
        container: the list we're testing for subsequence inclusion.
        subsequence: the list we hope will be a subsequence of container.
        msg: Optional message to report on failure.
      """
      first_nonmatching = None
      reversed_container = list(reversed(container))
      subsequence = list(subsequence)
  
      for e in subsequence:
        if e not in reversed_container:
          first_nonmatching = e
          break
        while e != reversed_container.pop():
          pass
  
      if first_nonmatching is not None:
        self.fail('%s not a subsequence of %s. First non-matching element: %s' %
                  (subsequence, container, first_nonmatching), msg)
  
    def assertContainsExactSubsequence(self, container, subsequence, msg=None):
      """Asserts that "container" contains "subsequence" as an exact subsequence.
  
      Asserts that "container" contains all the elements of "subsequence", in
      order, and without other elements interspersed. For example, [1, 2, 3] is an
      exact subsequence of [0, 0, 1, 2, 3, 0] but not of [0, 0, 1, 2, 0, 3, 0].
  
      Args:
        container: the list we're testing for subsequence inclusion.
        subsequence: the list we hope will be an exact subsequence of container.
        msg: Optional message to report on failure.
      """
      container = list(container)
      subsequence = list(subsequence)
      longest_match = 0
  
      for start in xrange(1 + len(container) - len(subsequence)):
        if longest_match == len(subsequence):
          break
        index = 0
        while (index < len(subsequence) and
               subsequence[index] == container[start + index]):
          index += 1
        longest_match = max(longest_match, index)
  
      if longest_match < len(subsequence):
        self.fail('%s not an exact subsequence of %s. '
                  'Longest matching prefix: %s' %
                  (subsequence, container, subsequence[:longest_match]), msg)
  
    def assertTotallyOrdered(self, *groups, **kwargs):
      """Asserts that total ordering has been implemented correctly.
  
      For example, say you have a class A that compares only on its attribute x.
      Comparators other than __lt__ are omitted for brevity.
  
      class A(object):
        def __init__(self, x, y):
          self.x = x
          self.y = y
  
        def __hash__(self):
          return hash(self.x)
  
        def __lt__(self, other):
          try:
            return self.x < other.x
          except AttributeError:
            return NotImplemented
  
      assertTotallyOrdered will check that instances can be ordered correctly.
      For example,
  
      self.assertTotallyOrdered(
        [None],  # None should come before everything else.
        [1],     # Integers sort earlier.
        [A(1, 'a')],
        [A(2, 'b')],  # 2 is after 1.
        [A(3, 'c'), A(3, 'd')],  # The second argument is irrelevant.
        [A(4, 'z')],
        ['foo'])  # Strings sort last.
  
      Args:
       *groups: A list of groups of elements.  Each group of elements is a list
           of objects that are equal.  The elements in each group must be less
           than the elements in the group after it.  For example, these groups are
           totally ordered: [None], [1], [2, 2], [3].
        **kwargs: optional msg keyword argument can be passed.
      """
  
      def CheckOrder(small, big):
        """Ensures small is ordered before big."""
        self.assertFalse(small == big,
                         self._formatMessage(msg, '%r unexpectedly equals %r' %
                                             (small, big)))
        self.assertTrue(small != big,
                        self._formatMessage(msg, '%r unexpectedly equals %r' %
                                            (small, big)))
        self.assertLess(small, big, msg)
        self.assertFalse(big < small,
                         self._formatMessage(msg,
                                             '%r unexpectedly less than %r' %
                                             (big, small)))
        self.assertLessEqual(small, big, msg)
        self.assertFalse(big <= small, self._formatMessage(
            '%r unexpectedly less than or equal to %r' % (big, small), msg
        ))
        self.assertGreater(big, small, msg)
        self.assertFalse(small > big,
                         self._formatMessage(msg,
                                             '%r unexpectedly greater than %r' %
                                             (small, big)))
        self.assertGreaterEqual(big, small)
        self.assertFalse(small >= big, self._formatMessage(
            msg,
            '%r unexpectedly greater than or equal to %r' % (small, big)))
  
      def CheckEqual(a, b):
        """Ensures that a and b are equal."""
        self.assertEqual(a, b, msg)
        self.assertFalse(a != b,
                         self._formatMessage(msg, '%r unexpectedly unequals %r' %
                                             (a, b)))
  
        # Objects that compare equal must hash to the same value, but this only
        # applies if both objects are hashable.
        if (isinstance(a, abc.Hashable) and
            isinstance(b, abc.Hashable)):
          self.assertEqual(
              hash(a), hash(b),
              self._formatMessage(
                  msg, 'hash %d of %r unexpectedly not equal to hash %d of %r' %
                  (hash(a), a, hash(b), b)))
  
        self.assertFalse(a < b,
                         self._formatMessage(msg,
                                             '%r unexpectedly less than %r' %
                                             (a, b)))
        self.assertFalse(b < a,
                         self._formatMessage(msg,
                                             '%r unexpectedly less than %r' %
                                             (b, a)))
        self.assertLessEqual(a, b, msg)
        self.assertLessEqual(b, a, msg)
        self.assertFalse(a > b,
                         self._formatMessage(msg,
                                             '%r unexpectedly greater than %r' %
                                             (a, b)))
        self.assertFalse(b > a,
                         self._formatMessage(msg,
                                             '%r unexpectedly greater than %r' %
                                             (b, a)))
        self.assertGreaterEqual(a, b, msg)
        self.assertGreaterEqual(b, a, msg)
  
      msg = kwargs.get('msg')
  
      # For every combination of elements, check the order of every pair of
      # elements.
      for elements in itertools.product(*groups):
        elements = list(elements)
        for index, small in enumerate(elements[:-1]):
          for big in elements[index + 1:]:
            CheckOrder(small, big)
  
      # Check that every element in each group is equal.
      for group in groups:
        for a in group:
          CheckEqual(a, a)
        for a, b in itertools.product(group, group):
          CheckEqual(a, b)
  
    def assertDictEqual(self, a, b, msg=None):
      """Raises AssertionError if a and b are not equal dictionaries.
  
      Args:
        a: A dict, the expected value.
        b: A dict, the actual value.
        msg: An optional str, the associated message.
  
      Raises:
        AssertionError: if the dictionaries are not equal.
      """
      self.assertIsInstance(a, dict, self._formatMessage(
          msg,
          'First argument is not a dictionary'
      ))
      self.assertIsInstance(b, dict, self._formatMessage(
          msg,
          'Second argument is not a dictionary'
      ))
  
      def Sorted(list_of_items):
        try:
          return sorted(list_of_items)  # In 3.3, unordered are possible.
        except TypeError:
          return list_of_items
  
      if a == b:
        return
      a_items = Sorted(list(six.iteritems(a)))
      b_items = Sorted(list(six.iteritems(b)))
  
      unexpected = []
      missing = []
      different = []
  
      safe_repr = unittest.util.safe_repr  # pytype: disable=module-attr
  
      def Repr(dikt):
        """Deterministic repr for dict."""
        # Sort the entries based on their repr, not based on their sort order,
        # which will be non-deterministic across executions, for many types.
        entries = sorted((safe_repr(k), safe_repr(v))
                         for k, v in six.iteritems(dikt))
        return '{%s}' % (', '.join('%s: %s' % pair for pair in entries))
  
      message = ['%s != %s%s' % (Repr(a), Repr(b), ' (%s)' % msg if msg else '')]
  
      # The standard library default output confounds lexical difference with
      # value difference; treat them separately.
      for a_key, a_value in a_items:
        if a_key not in b:
          missing.append((a_key, a_value))
        elif a_value != b[a_key]:
          different.append((a_key, a_value, b[a_key]))
  
      for b_key, b_value in b_items:
        if b_key not in a:
          unexpected.append((b_key, b_value))
  
      if unexpected:
        message.append(
            'Unexpected, but present entries:\n%s' % ''.join(
                '%s: %s\n' % (safe_repr(k), safe_repr(v)) for k, v in unexpected))
  
      if different:
        message.append(
            'repr() of differing entries:\n%s' % ''.join(
                '%s: %s != %s\n' % (safe_repr(k), safe_repr(a_value),
                                    safe_repr(b_value))
                for k, a_value, b_value in different))
  
      if missing:
        message.append(
            'Missing entries:\n%s' % ''.join(
                ('%s: %s\n' % (safe_repr(k), safe_repr(v)) for k, v in missing)))
  
      raise self.failureException('\n'.join(message))
  
    def assertUrlEqual(self, a, b, msg=None):
      """Asserts that urls are equal, ignoring ordering of query params."""
      parsed_a = urllib.parse.urlparse(a)
      parsed_b = urllib.parse.urlparse(b)
      self.assertEqual(parsed_a.scheme, parsed_b.scheme, msg)
      self.assertEqual(parsed_a.netloc, parsed_b.netloc, msg)
      self.assertEqual(parsed_a.path, parsed_b.path, msg)
      self.assertEqual(parsed_a.fragment, parsed_b.fragment, msg)
      self.assertEqual(sorted(parsed_a.params.split(';')),
                       sorted(parsed_b.params.split(';')), msg)
      self.assertDictEqual(
          urllib.parse.parse_qs(parsed_a.query, keep_blank_values=True),
          urllib.parse.parse_qs(parsed_b.query, keep_blank_values=True), msg)
  
    def assertSameStructure(self, a, b, aname='a', bname='b', msg=None):
      """Asserts that two values contain the same structural content.
  
      The two arguments should be data trees consisting of trees of dicts and
      lists. They will be deeply compared by walking into the contents of dicts
      and lists; other items will be compared using the == operator.
      If the two structures differ in content, the failure message will indicate
      the location within the structures where the first difference is found.
      This may be helpful when comparing large structures.
  
      Mixed Sequence and Set types are supported. Mixed Mapping types are
      supported, but the order of the keys will not be considered in the
      comparison.
  
      Args:
        a: The first structure to compare.
        b: The second structure to compare.
        aname: Variable name to use for the first structure in assertion messages.
        bname: Variable name to use for the second structure.
        msg: Additional text to include in the failure message.
      """
  
      # Accumulate all the problems found so we can report all of them at once
      # rather than just stopping at the first
      problems = []
  
      _walk_structure_for_problems(a, b, aname, bname, problems)
  
      # Avoid spamming the user toooo much
      if self.maxDiff is not None:
        max_problems_to_show = self.maxDiff // 80
        if len(problems) > max_problems_to_show:
          problems = problems[0:max_problems_to_show-1] + ['...']
  
      if problems:
        self.fail('; '.join(problems), msg)
  
    def assertJsonEqual(self, first, second, msg=None):
      """Asserts that the JSON objects defined in two strings are equal.
  
      A summary of the differences will be included in the failure message
      using assertSameStructure.
  
      Args:
        first: A string containing JSON to decode and compare to second.
        second: A string containing JSON to decode and compare to first.
        msg: Additional text to include in the failure message.
      """
      try:
        first_structured = json.loads(first)
      except ValueError as e:
        raise ValueError(self._formatMessage(
            msg,
            'could not decode first JSON value %s: %s' % (first, e)))
  
      try:
        second_structured = json.loads(second)
      except ValueError as e:
        raise ValueError(self._formatMessage(
            msg,
            'could not decode second JSON value %s: %s' % (second, e)))
  
      self.assertSameStructure(first_structured, second_structured,
                               aname='first', bname='second', msg=msg)
  
    def _getAssertEqualityFunc(self, first, second):
      # type: (Any, Any) -> Callable[..., None]
      try:
        return super(TestCase, self)._getAssertEqualityFunc(first, second)
      except AttributeError:
        # This is a workaround if unittest.TestCase.__init__ was never run.
        # It usually means that somebody created a subclass just for the
        # assertions and has overridden __init__. "assertTrue" is a safe
        # value that will not make __init__ raise a ValueError.
        test_method = getattr(self, '_testMethodName', 'assertTrue')
        super(TestCase, self).__init__(test_method)
  
      return super(TestCase, self)._getAssertEqualityFunc(first, second)
  
    def fail(self, msg=None, prefix=None):
      """Fail immediately with the given message, optionally prefixed."""
      return super(TestCase, self).fail(self._formatMessage(prefix, msg))
  
  
  def _sorted_list_difference(expected, actual):
    # type: (List[_T], List[_T]) -> Tuple[List[_T], List[_T]]
    """Finds elements in only one or the other of two, sorted input lists.
  
    Returns a two-element tuple of lists.  The first list contains those
    elements in the "expected" list but not in the "actual" list, and the
    second contains those elements in the "actual" list but not in the
    "expected" list.  Duplicate elements in either input list are ignored.
  
    Args:
      expected:  The list we expected.
      actual:  The list we actualy got.
    Returns:
      (missing, unexpected)
      missing: items in expected that are not in actual.
      unexpected: items in actual that are not in expected.
    """
    i = j = 0
    missing = []
    unexpected = []
    while True:
      try:
        e = expected[i]
        a = actual[j]
        if e < a:
          missing.append(e)
          i += 1
          while expected[i] == e:
            i += 1
        elif e > a:
          unexpected.append(a)
          j += 1
          while actual[j] == a:
            j += 1
        else:
          i += 1
          try:
            while expected[i] == e:
              i += 1
          finally:
            j += 1
            while actual[j] == a:
              j += 1
      except IndexError:
        missing.extend(expected[i:])
        unexpected.extend(actual[j:])
        break
    return missing, unexpected
  
  
  def _are_both_of_integer_type(a, b):
    # type: (object, object) -> bool
    return isinstance(a, six.integer_types) and isinstance(b, six.integer_types)
  
  
  def _are_both_of_sequence_type(a, b):
    # type: (object, object) -> bool
    return isinstance(a, abc.Sequence) and isinstance(
        b, abc.Sequence) and not isinstance(
            a, _TEXT_OR_BINARY_TYPES) and not isinstance(b, _TEXT_OR_BINARY_TYPES)
  
  
  def _are_both_of_set_type(a, b):
    # type: (object, object) -> bool
    return isinstance(a, abc.Set) and isinstance(b, abc.Set)
  
  
  def _are_both_of_mapping_type(a, b):
    # type: (object, object) -> bool
    return isinstance(a, abc.Mapping) and isinstance(
        b, abc.Mapping)
  
  
  def _walk_structure_for_problems(a, b, aname, bname, problem_list):
    """The recursive comparison behind assertSameStructure."""
    if type(a) != type(b) and not (  # pylint: disable=unidiomatic-typecheck
        _are_both_of_integer_type(a, b) or _are_both_of_sequence_type(a, b) or
        _are_both_of_set_type(a, b) or _are_both_of_mapping_type(a, b)):
      # We do not distinguish between int and long types as 99.99% of Python 2
      # code should never care.  They collapse into a single type in Python 3.
      problem_list.append('%s is a %r but %s is a %r' %
                          (aname, type(a), bname, type(b)))
      # If they have different types there's no point continuing
      return
  
    if isinstance(a, abc.Set):
      for k in a:
        if k not in b:
          problem_list.append(
              '%s has %r but %s does not' % (aname, k, bname))
      for k in b:
        if k not in a:
          problem_list.append('%s lacks %r but %s has it' % (aname, k, bname))
  
    # NOTE: a or b could be a defaultdict, so we must take care that the traversal
    # doesn't modify the data.
    elif isinstance(a, abc.Mapping):
      for k in a:
        if k in b:
          _walk_structure_for_problems(
              a[k], b[k], '%s[%r]' % (aname, k), '%s[%r]' % (bname, k),
              problem_list)
        else:
          problem_list.append(
              "%s has [%r] with value %r but it's missing in %s" %
              (aname, k, a[k], bname))
      for k in b:
        if k not in a:
          problem_list.append(
              '%s lacks [%r] but %s has it with value %r' %
              (aname, k, bname, b[k]))
  
    # Strings/bytes are Sequences but we'll just do those with regular !=
    elif (isinstance(a, abc.Sequence) and
          not isinstance(a, _TEXT_OR_BINARY_TYPES)):
      minlen = min(len(a), len(b))
      for i in xrange(minlen):
        _walk_structure_for_problems(
            a[i], b[i], '%s[%d]' % (aname, i), '%s[%d]' % (bname, i),
            problem_list)
      for i in xrange(minlen, len(a)):
        problem_list.append('%s has [%i] with value %r but %s does not' %
                            (aname, i, a[i], bname))
      for i in xrange(minlen, len(b)):
        problem_list.append('%s lacks [%i] but %s has it with value %r' %
                            (aname, i, bname, b[i]))
  
    else:
      if a != b:
        problem_list.append('%s is %r but %s is %r' % (aname, a, bname, b))
  
  
  def get_command_string(command):
    """Returns an escaped string that can be used as a shell command.
  
    Args:
      command: List or string representing the command to run.
    Returns:
      A string suitable for use as a shell command.
    """
    if isinstance(command, six.string_types):
      return command
    else:
      if os.name == 'nt':
        return ' '.join(command)
      else:
        # The following is identical to Python 3's shlex.quote function.
        command_string = ''
        for word in command:
          # Single quote word, and replace each ' in word with '"'"'
          command_string += "'" + word.replace("'", "'\"'\"'") + "' "
        return command_string[:-1]
  
  
  def get_command_stderr(command, env=None, close_fds=True):
    """Runs the given shell command and returns a tuple.
  
    Args:
      command: List or string representing the command to run.
      env: Dictionary of environment variable settings. If None, no environment
          variables will be set for the child process. This is to make tests
          more hermetic. NOTE: this behavior is different than the standard
          subprocess module.
      close_fds: Whether or not to close all open fd's in the child after forking.
          On Windows, this is ignored and close_fds is always False.
  
    Returns:
      Tuple of (exit status, text printed to stdout and stderr by the command).
    """
    if env is None: env = {}
    if os.name == 'nt':
      # Windows does not support setting close_fds to True while also redirecting
      # standard handles.
      close_fds = False
  
    use_shell = isinstance(command, six.string_types)
    process = subprocess.Popen(
        command,
        close_fds=close_fds,
        env=env,
        shell=use_shell,
        stderr=subprocess.STDOUT,
        stdout=subprocess.PIPE)
    output = process.communicate()[0]
    exit_status = process.wait()
    return (exit_status, output)
  
  
  def _quote_long_string(s):
    # type: (Union[Text, bytes, bytearray]) -> Text
    """Quotes a potentially multi-line string to make the start and end obvious.
  
    Args:
      s: A string.
  
    Returns:
      The quoted string.
    """
    if isinstance(s, (bytes, bytearray)):
      try:
        s = s.decode('utf-8')
      except UnicodeDecodeError:
        s = str(s)
    return ('8<-----------\n' +
            s + '\n' +
            '----------->8\n')
  
  
  class _TestProgramManualRun(unittest.TestProgram):
    """A TestProgram which runs the tests manually."""
  
    def runTests(self, do_run=False):
      """Runs the tests."""
      if do_run:
        unittest.TestProgram.runTests(self)
  
  
  def print_python_version():
    # type: () -> None
    # Having this in the test output logs by default helps debugging when all
    # you've got is the log and no other idea of which Python was used.
    sys.stderr.write('Running tests under Python {0[0]}.{0[1]}.{0[2]}: '
                     '{1}\n'.format(
                         sys.version_info,
                         sys.executable if sys.executable else 'embedded.'))
  
  
  def main(*args, **kwargs):
    # type: (Text, Mapping[Text, Any]) -> None
    """Executes a set of Python unit tests.
  
    Usually this function is called without arguments, so the
    unittest.TestProgram instance will get created with the default settings,
    so it will run all test methods of all TestCase classes in the __main__
    module.
  
    Args:
      *args: Positional arguments passed through to unittest.TestProgram.__init__.
      **kwargs: Keyword arguments passed through to unittest.TestProgram.__init__.
    """
    print_python_version()
    _run_in_app(run_tests, args, kwargs)
  
  
  def _is_in_app_main():
    # type: () -> bool
    """Returns True iff app.run is active."""
    f = sys._getframe().f_back  # pylint: disable=protected-access
    while f:
      if f.f_code == six.get_function_code(app.run):  # pytype: disable=wrong-arg-types
        return True
      f = f.f_back
    return False
  
  
  class _SavedFlag(object):
    """Helper class for saving and restoring a flag value."""
  
    def __init__(self, flag):
      self.flag = flag
      self.value = flag.value
      self.present = flag.present
  
    def restore_flag(self):
      self.flag.value = self.value
      self.flag.present = self.present
  
  
  def _register_sigterm_with_faulthandler():
    # type: () -> None
    """Have faulthandler dump stacks on SIGTERM.  Useful to diagnose timeouts."""
    if faulthandler and getattr(faulthandler, 'register', None):
      # faulthandler.register is not avaiable on Windows.
      # faulthandler.enable() is already called by app.run.
      try:
        faulthandler.register(signal.SIGTERM, chain=True)  # pytype: disable=module-attr
      except Exception as e:  # pylint: disable=broad-except
        sys.stderr.write('faulthandler.register(SIGTERM) failed '
                         '%r; ignoring.\n' % e)
  
  
  def _run_in_app(function, args, kwargs):
    # type: (Callable[..., None], Sequence[Text], Mapping[Text, Any]) -> None
    """Executes a set of Python unit tests, ensuring app.run.
  
    This is a private function, users should call absltest.main().
  
    _run_in_app calculates argv to be the command-line arguments of this program
    (without the flags), sets the default of FLAGS.alsologtostderr to True,
    then it calls function(argv, args, kwargs), making sure that `function'
    will get called within app.run(). _run_in_app does this by checking whether
    it is called by app.run(), or by calling app.run() explicitly.
  
    The reason why app.run has to be ensured is to make sure that
    flags are parsed and stripped properly, and other initializations done by
    the app module are also carried out, no matter if absltest.run() is called
    from within or outside app.run().
  
    If _run_in_app is called from within app.run(), then it will reparse
    sys.argv and pass the result without command-line flags into the argv
    argument of `function'. The reason why this parsing is needed is that
    __main__.main() calls absltest.main() without passing its argv. So the
    only way _run_in_app could get to know the argv without the flags is that
    it reparses sys.argv.
  
    _run_in_app changes the default of FLAGS.alsologtostderr to True so that the
    test program's stderr will contain all the log messages unless otherwise
    specified on the command-line. This overrides any explicit assignment to
    FLAGS.alsologtostderr by the test program prior to the call to _run_in_app()
    (e.g. in __main__.main).
  
    Please note that _run_in_app (and the function it calls) is allowed to make
    changes to kwargs.
  
    Args:
      function: absltest.run_tests or a similar function. It will be called as
          function(argv, args, kwargs) where argv is a list containing the
          elements of sys.argv without the command-line flags.
      args: Positional arguments passed through to unittest.TestProgram.__init__.
      kwargs: Keyword arguments passed through to unittest.TestProgram.__init__.
    """
    if _is_in_app_main():
      _register_sigterm_with_faulthandler()
  
      # Save command-line flags so the side effects of FLAGS(sys.argv) can be
      # undone.
      flag_objects = (FLAGS[name] for name in FLAGS)
      saved_flags = dict((f.name, _SavedFlag(f)) for f in flag_objects)
  
      # Change the default of alsologtostderr from False to True, so the test
      # programs's stderr will contain all the log messages.
      # If --alsologtostderr=false is specified in the command-line, or user
      # has called FLAGS.alsologtostderr = False before, then the value is kept
      # False.
      FLAGS.set_default('alsologtostderr', True)
      # Remove it from saved flags so it doesn't get restored later.
      del saved_flags['alsologtostderr']
  
      # The call FLAGS(sys.argv) parses sys.argv, returns the arguments
      # without the flags, and -- as a side effect -- modifies flag values in
      # FLAGS. We don't want the side effect, because we don't want to
      # override flag changes the program did (e.g. in __main__.main)
      # after the command-line has been parsed. So we have the for loop below
      # to change back flags to their old values.
      argv = FLAGS(sys.argv)
      for saved_flag in six.itervalues(saved_flags):
        saved_flag.restore_flag()
  
      function(argv, args, kwargs)
    else:
      # Send logging to stderr. Use --alsologtostderr instead of --logtostderr
      # in case tests are reading their own logs.
      FLAGS.set_default('alsologtostderr', True)
  
      def main_function(argv):
        _register_sigterm_with_faulthandler()
        function(argv, args, kwargs)
  
      app.run(main=main_function)
  
  
  def _is_suspicious_attribute(testCaseClass, name):
    # type: (Type, Text) -> bool
    """Returns True if an attribute is a method named like a test method."""
    if name.startswith('Test') and len(name) > 4 and name[4].isupper():
      attr = getattr(testCaseClass, name)
      if inspect.isfunction(attr) or inspect.ismethod(attr):
        args = inspect.getargspec(attr)
        return (len(args.args) == 1 and args.args[0] == 'self'
                and args.varargs is None and args.keywords is None)
    return False
  
  
  class TestLoader(unittest.TestLoader):
    """A test loader which supports common test features.
  
    Supported features include:
     * Banning untested methods with test-like names: methods attached to this
       testCase with names starting with `Test` are ignored by the test runner,
       and often represent mistakenly-omitted test cases. This loader will raise
       a TypeError when attempting to load a TestCase with such methods.
     * Randomization of test case execution order (optional).
    """
  
    _ERROR_MSG = textwrap.dedent("""Method '%s' is named like a test case but
    is not one. This is often a bug. If you want it to be a test method,
    name it with 'test' in lowercase. If not, rename the method to not begin
    with 'Test'.""")
  
    def __init__(self, *args, **kwds):
      super(TestLoader, self).__init__(*args, **kwds)
      seed = _get_default_randomize_ordering_seed()
      if seed:
        self._seed = seed
        self._random = random.Random(self._seed)
      else:
        self._seed = None
        self._random = None
  
    def getTestCaseNames(self, testCaseClass):  # pylint:disable=invalid-name
      """Validates and returns a (possibly randomized) list of test case names."""
      for name in dir(testCaseClass):
        if _is_suspicious_attribute(testCaseClass, name):
          raise TypeError(TestLoader._ERROR_MSG % name)
      names = super(TestLoader, self).getTestCaseNames(testCaseClass)
      if self._seed is not None:
        logging.info('Randomizing test order with seed: %d', self._seed)
        logging.info('To reproduce this order, re-run with '
                     '--test_randomize_ordering_seed=%d', self._seed)
        self._random.shuffle(names)
      return names
  
  
  def get_default_xml_output_filename():
    # type: () -> Optional[Text]
    if os.environ.get('XML_OUTPUT_FILE'):
      return os.environ['XML_OUTPUT_FILE']
    elif os.environ.get('RUNNING_UNDER_TEST_DAEMON'):
      return os.path.join(os.path.dirname(FLAGS.test_tmpdir), 'test_detail.xml')
    elif os.environ.get('TEST_XMLOUTPUTDIR'):
      return os.path.join(
          os.environ['TEST_XMLOUTPUTDIR'],
          os.path.splitext(os.path.basename(sys.argv[0]))[0] + '.xml')
  
  
  def _setup_filtering(argv):
    # type: (MutableSequence[Text]) -> None
    """Implements the bazel test filtering protocol.
  
    The following environment variable is used in this method:
  
      TESTBRIDGE_TEST_ONLY: string, if set, is forwarded to the unittest
        framework to use as a test filter. Its value is split with shlex
        before being passed as positional arguments on argv.
  
    Args:
      argv: the argv to mutate in-place.
    """
    test_filter = os.environ.get('TESTBRIDGE_TEST_ONLY')
    if argv is None or not test_filter:
      return
  
    argv[1:1] = shlex.split(test_filter)
  
  
  def _setup_sharding(custom_loader=None):
    # type: (Optional[unittest.TestLoader]) -> unittest.TestLoader
    """Implements the bazel sharding protocol.
  
    The following environment variables are used in this method:
  
      TEST_SHARD_STATUS_FILE: string, if set, points to a file. We write a blank
        file to tell the test runner that this test implements the test sharding
        protocol.
  
      TEST_TOTAL_SHARDS: int, if set, sharding is requested.
  
      TEST_SHARD_INDEX: int, must be set if TEST_TOTAL_SHARDS is set. Specifies
        the shard index for this instance of the test process. Must satisfy:
        0 <= TEST_SHARD_INDEX < TEST_TOTAL_SHARDS.
  
    Args:
      custom_loader: A TestLoader to be made sharded.
  
    Returns:
      The test loader for shard-filtering or the standard test loader, depending
      on the sharding environment variables.
    """
  
    # It may be useful to write the shard file even if the other sharding
    # environment variables are not set. Test runners may use this functionality
    # to query whether a test binary implements the test sharding protocol.
    if 'TEST_SHARD_STATUS_FILE' in os.environ:
      try:
        f = None
        try:
          f = open(os.environ['TEST_SHARD_STATUS_FILE'], 'w')
          f.write('')
        except IOError:
          sys.stderr.write('Error opening TEST_SHARD_STATUS_FILE (%s). Exiting.'
                           % os.environ['TEST_SHARD_STATUS_FILE'])
          sys.exit(1)
      finally:
        if f is not None: f.close()
  
    base_loader = custom_loader or TestLoader()
    if 'TEST_TOTAL_SHARDS' not in os.environ:
      # Not using sharding, use the expected test loader.
      return base_loader
  
    total_shards = int(os.environ['TEST_TOTAL_SHARDS'])
    shard_index = int(os.environ['TEST_SHARD_INDEX'])
  
    if shard_index < 0 or shard_index >= total_shards:
      sys.stderr.write('ERROR: Bad sharding values. index=%d, total=%d\n' %
                       (shard_index, total_shards))
      sys.exit(1)
  
    # Replace the original getTestCaseNames with one that returns
    # the test case names for this shard.
    delegate_get_names = base_loader.getTestCaseNames
  
    bucket_iterator = itertools.cycle(xrange(total_shards))
  
    def getShardedTestCaseNames(testCaseClass):
      filtered_names = []
      for testcase in sorted(delegate_get_names(testCaseClass)):
        bucket = next(bucket_iterator)
        if bucket == shard_index:
          filtered_names.append(testcase)
      return filtered_names
  
    base_loader.getTestCaseNames = getShardedTestCaseNames
    return base_loader
  
  
  # pylint: disable=line-too-long
  def _run_and_get_tests_result(argv, args, kwargs, xml_test_runner_class):
    # type: (MutableSequence[Text], Sequence[Any], MutableMapping[Text, Any], Type) -> unittest.TestResult
    # pylint: enable=line-too-long
    """Executes a set of Python unit tests and returns the result."""
  
    # Set up test filtering if requested in environment.
    _setup_filtering(argv)
  
    # Shard the (default or custom) loader if sharding is turned on.
    kwargs['testLoader'] = _setup_sharding(kwargs.get('testLoader', None))
  
    # XML file name is based upon (sorted by priority):
    # --xml_output_file flag, XML_OUTPUT_FILE variable,
    # TEST_XMLOUTPUTDIR variable or RUNNING_UNDER_TEST_DAEMON variable.
    if not FLAGS.xml_output_file:
      FLAGS.xml_output_file = get_default_xml_output_filename()
    xml_output_file = FLAGS.xml_output_file
  
    xml_buffer = None
    if xml_output_file:
      xml_output_dir = os.path.dirname(xml_output_file)
      if xml_output_dir and not os.path.isdir(xml_output_dir):
        try:
          os.makedirs(xml_output_dir)
        except OSError as e:
          # File exists error can occur with concurrent tests
          if e.errno != errno.EEXIST:
            raise
      # Fail early if we can't write to the XML output file. This is so that we
      # don't waste people's time running tests that will just fail anyways.
      with _open(xml_output_file, 'w'):
        pass
  
      # We can reuse testRunner if it supports XML output (e. g. by inheriting
      # from xml_reporter.TextAndXMLTestRunner). Otherwise we need to use
      # xml_reporter.TextAndXMLTestRunner.
      if (kwargs.get('testRunner') is not None
          and not hasattr(kwargs['testRunner'], 'set_default_xml_stream')):
        sys.stderr.write('WARNING: XML_OUTPUT_FILE or --xml_output_file setting '
                         'overrides testRunner=%r setting (possibly from --pdb)'
                         % (kwargs['testRunner']))
        # Passing a class object here allows TestProgram to initialize
        # instances based on its kwargs and/or parsed command-line args.
        kwargs['testRunner'] = xml_test_runner_class
      if kwargs.get('testRunner') is None:
        kwargs['testRunner'] = xml_test_runner_class
      # Use an in-memory buffer (not backed by the actual file) to store the XML
      # report, because some tools modify the file (e.g., create a placeholder
      # with partial information, in case the test process crashes).
      xml_buffer = six.StringIO()
      kwargs['testRunner'].set_default_xml_stream(xml_buffer)  # pytype: disable=attribute-error
    elif kwargs.get('testRunner') is None:
      kwargs['testRunner'] = _pretty_print_reporter.TextTestRunner
  
    if FLAGS.pdb_post_mortem:
      runner = kwargs['testRunner']
      # testRunner can be a class or an instance, which must be tested for
      # differently.
      # Overriding testRunner isn't uncommon, so only enable the debugging
      # integration if the runner claims it does; we don't want to accidentally
      # clobber something on the runner.
      if ((isinstance(runner, type) and
           issubclass(runner, _pretty_print_reporter.TextTestRunner)) or
          isinstance(runner, _pretty_print_reporter.TextTestRunner)):
        runner.run_for_debugging = True
  
    # Make sure tmpdir exists.
    if not os.path.isdir(FLAGS.test_tmpdir):
      try:
        os.makedirs(FLAGS.test_tmpdir)
      except OSError as e:
        # Concurrent test might have created the directory.
        if e.errno != errno.EEXIST:
          raise
  
    # Let unittest.TestProgram.__init__ do its own argv parsing, e.g. for '-v',
    # on argv, which is sys.argv without the command-line flags.
    kwargs.setdefault('argv', argv)
  
    try:
      test_program = unittest.TestProgram(*args, **kwargs)
      return test_program.result
    finally:
      if xml_buffer:
        try:
          with _open(xml_output_file, 'w') as f:
            f.write(xml_buffer.getvalue())
        finally:
          xml_buffer.close()
  
  
  def run_tests(argv, args, kwargs):  # pylint: disable=line-too-long
    # type: (MutableSequence[Text], Sequence[Any], MutableMapping[Text, Any]) -> None
    # pylint: enable=line-too-long
    """Executes a set of Python unit tests.
  
    Most users should call absltest.main() instead of run_tests.
  
    Please note that run_tests should be called from app.run.
    Calling absltest.main() would ensure that.
  
    Please note that run_tests is allowed to make changes to kwargs.
  
    Args:
      argv: sys.argv with the command-line flags removed from the front, i.e. the
        argv with which app.run() has called __main__.main.
      args: Positional arguments passed through to unittest.TestProgram.__init__.
      kwargs: Keyword arguments passed through to unittest.TestProgram.__init__.
    """
    result = _run_and_get_tests_result(
        argv, args, kwargs, xml_reporter.TextAndXMLTestRunner)
    sys.exit(not result.wasSuccessful())
  
  
  def _get_qualname(cls):
    # type: (Type) -> Text
    if six.PY3:
      name = cls.__qualname__
    else:
      name = '{}.{}'.format(cls.__module__, cls.__name__)
    return name.replace('__main__.', '')
  
  
  def _rmtree_ignore_errors(path):
    # type: (Text) -> None
    if os.path.isfile(path):
      os.unlink(path)
    else:
      shutil.rmtree(path, ignore_errors=True)
  
  
  def _makedirs_exist_ok(dir_name):
    # type: (Text) -> None
    if six.PY3:
      os.makedirs(dir_name, exist_ok=True)  # pylint: disable=unexpected-keyword-arg
    else:
      # Python 2 doesn't have the exist_ok arg, so we roll it ourselves
      try:
        os.makedirs(dir_name)
      except OSError as e:
        if e.errno != errno.EEXIST:
          raise
  
  
  def _get_first_part(path):
    # type: (Text) -> Text
    parts = path.split(os.sep, 1)
    return parts[0]
  