# Source code for unittest.case

    """Test case implementation"""

    import sys
    import functools
    import difflib
    import pprint
    import re
    import warnings
    import collections
    import contextlib
    import traceback
    import time
    import types

    from . import result
    from .util import (strclass, safe_repr, _count_diff_all_purpose,
                       _count_diff_hashable, _common_shorten_repr)

    __unittest = True

    _subtest_msg_sentinel = object()

    DIFF_OMITTED = ('\nDiff is %s characters long. '
                     'Set self.maxDiff to None to see it.')

    class SkipTest(Exception):
        """
        Raise this exception in a test to skip it.

        Usually you can use TestCase.skipTest() or one of the skipping decorators
        instead of raising this directly.
        """

    class _ShouldStop(Exception):
        """
        The test should stop.
        """

    class _UnexpectedSuccess(Exception):
        """
        The test was supposed to fail, but it didn't!
        """

    class _Outcome(object):
        def __init__(self, result=None):
            self.expecting_failure = False
            self.result = result
            self.result_supports_subtests = hasattr(result, "addSubTest")
            self.success = True
            self.expectedFailure = None

        @contextlib.contextmanager
        def testPartExecutor(self, test_case, subTest=False):
            old_success = self.success
            self.success = True
            try:
                yield
            except KeyboardInterrupt:
                raise
            except SkipTest as e:
                self.success = False
                _addSkip(self.result, test_case, str(e))
            except _ShouldStop:
                pass
            except:
                exc_info = sys.exc_info()
                if self.expecting_failure:
                    self.expectedFailure = exc_info
                else:
                    self.success = False
                    if subTest:
                        self.result.addSubTest(test_case.test_case, test_case, exc_info)
                    else:
                        _addError(self.result, test_case, exc_info)
                # explicitly break a reference cycle:
                # exc_info -> frame -> exc_info
                exc_info = None
            else:
                if subTest and self.success:
                    self.result.addSubTest(test_case.test_case, test_case, None)
            finally:
                self.success = self.success and old_success

    def _addSkip(result, test_case, reason):
        addSkip = getattr(result, 'addSkip', None)
        if addSkip is not None:
            addSkip(test_case, reason)
        else:
            warnings.warn("TestResult has no addSkip method, skips not reported",
                          RuntimeWarning, 2)
            result.addSuccess(test_case)

    def _addError(result, test, exc_info):
        if result is not None and exc_info is not None:
            if issubclass(exc_info[0], test.failureException):
                result.addFailure(test, exc_info)
            else:
                result.addError(test, exc_info)

    def _id(obj):
        return obj

    def _enter_context(cm, addcleanup):
        # We look up the special methods on the type to match the with
        # statement.
        cls = type(cm)
        try:
            enter = cls.__enter__
            exit = cls.__exit__
        except AttributeError:
            raise TypeError(f"'{cls.__module__}.{cls.__qualname__}' object does "
                            f"not support the context manager protocol") from None
        result = enter(cm)
        addcleanup(exit, cm, None, None, None)
        return result

    _module_cleanups = []
    def addModuleCleanup(function, /, *args, **kwargs):
        """Same as addCleanup, except the cleanup items are called even if
        setUpModule fails (unlike tearDownModule)."""
        _module_cleanups.append((function, args, kwargs))

    def enterModuleContext(cm):
        """Same as enterContext, but module-wide."""
        return _enter_context(cm, addModuleCleanup)

    def doModuleCleanups():
        """Execute all module cleanup functions. Normally called for you after
        tearDownModule."""
        exceptions = []
        while _module_cleanups:
            function, args, kwargs = _module_cleanups.pop()
            try:
                function(*args, **kwargs)
            except Exception as exc:
                exceptions.append(exc)
        if exceptions:
            # Swallows all but first exception. If a multi-exception handler
            # gets written we should use that here instead.
            raise exceptions[0]

    def skip(reason):
        """
        Unconditionally skip a test.
        """
        def decorator(test_item):
            if not isinstance(test_item, type):
                @functools.wraps(test_item)
                def skip_wrapper(*args, **kwargs):
                    raise SkipTest(reason)
                test_item = skip_wrapper

            test_item.__unittest_skip__ = True
            test_item.__unittest_skip_why__ = reason
            return test_item
        if isinstance(reason, types.FunctionType):
            test_item = reason
            reason = ''
            return decorator(test_item)
        return decorator

    def skipIf(condition, reason):
        """
        Skip a test if the condition is true.
        """
        if condition:
            return skip(reason)
        return _id

    def skipUnless(condition, reason):
        """
        Skip a test unless the condition is true.
        """
        if not condition:
            return skip(reason)
        return _id

    def expectedFailure(test_item):
        test_item.__unittest_expecting_failure__ = True
        return test_item

    def _is_subtype(expected, basetype):
        if isinstance(expected, tuple):
            return all(_is_subtype(e, basetype) for e in expected)
        return isinstance(expected, type) and issubclass(expected, basetype)

    class _BaseTestCaseContext:

        def __init__(self, test_case):
            self.test_case = test_case

        def _raiseFailure(self, standardMsg):
            msg = self.test_case._formatMessage(self.msg, standardMsg)
            raise self.test_case.failureException(msg)

    class _AssertRaisesBaseContext(_BaseTestCaseContext):

        def __init__(self, expected, test_case, expected_regex=None):
            _BaseTestCaseContext.__init__(self, test_case)
            self.expected = expected
            self.test_case = test_case
            if expected_regex is not None:
                expected_regex = re.compile(expected_regex)
            self.expected_regex = expected_regex
            self.obj_name = None
            self.msg = None

        def handle(self, name, args, kwargs):
            """
            If args is empty, assertRaises/Warns is being used as a
            context manager, so check for a 'msg' kwarg and return self.
            If args is not empty, call a callable passing positional and keyword
            arguments.
            """
            try:
                if not _is_subtype(self.expected, self._base_type):
                    raise TypeError('%s() arg 1 must be %s' %
                                    (name, self._base_type_str))
                if not args:
                    self.msg = kwargs.pop('msg', None)
                    if kwargs:
                        raise TypeError('%r is an invalid keyword argument for '
                                        'this function' % (next(iter(kwargs)),))
                    return self

                callable_obj, *args = args
                try:
                    self.obj_name = callable_obj.__name__
                except AttributeError:
                    self.obj_name = str(callable_obj)
                with self:
                    callable_obj(*args, **kwargs)
            finally:
                # bpo-23890: manually break a reference cycle
                self = None

    class _AssertRaisesContext(_AssertRaisesBaseContext):
        """A context manager used to implement TestCase.assertRaises* methods."""

        _base_type = BaseException
        _base_type_str = 'an exception type or tuple of exception types'

        def __enter__(self):
            return self

        def __exit__(self, exc_type, exc_value, tb):
            if exc_type is None:
                try:
                    exc_name = self.expected.__name__
                except AttributeError:
                    exc_name = str(self.expected)
                if self.obj_name:
                    self._raiseFailure("{} not raised by {}".format(exc_name,
                                                                    self.obj_name))
                else:
                    self._raiseFailure("{} not raised".format(exc_name))
            else:
                traceback.clear_frames(tb)
            if not issubclass(exc_type, self.expected):
                # let unexpected exceptions pass through
                return False
            # store exception, without traceback, for later retrieval
            self.exception = exc_value.with_traceback(None)
            if self.expected_regex is None:
                return True

            expected_regex = self.expected_regex
            if not expected_regex.search(str(exc_value)):
                self._raiseFailure('"{}" does not match "{}"'.format(
                         expected_regex.pattern, str(exc_value)))
            return True

        __class_getitem__ = classmethod(types.GenericAlias)

    class _AssertWarnsContext(_AssertRaisesBaseContext):
        """A context manager used to implement TestCase.assertWarns* methods."""

        _base_type = Warning
        _base_type_str = 'a warning type or tuple of warning types'

        def __enter__(self):
            # The __warningregistry__'s need to be in a pristine state for tests
            # to work properly.
            for v in list(sys.modules.values()):
                if getattr(v, '__warningregistry__', None):
                    v.__warningregistry__ = {}
            self.warnings_manager = warnings.catch_warnings(record=True)
            self.warnings = self.warnings_manager.__enter__()
            warnings.simplefilter("always", self.expected)
            return self

        def __exit__(self, exc_type, exc_value, tb):
            self.warnings_manager.__exit__(exc_type, exc_value, tb)
            if exc_type is not None:
                # let unexpected exceptions pass through
                return
            try:
                exc_name = self.expected.__name__
            except AttributeError:
                exc_name = str(self.expected)
            first_matching = None
            for m in self.warnings:
                w = m.message
                if not isinstance(w, self.expected):
                    continue
                if first_matching is None:
                    first_matching = w
                if (self.expected_regex is not None and
                    not self.expected_regex.search(str(w))):
                    continue
                # store warning for later retrieval
                self.warning = w
                self.filename = m.filename
                self.lineno = m.lineno
                return
            # Now we simply try to choose a helpful failure message
            if first_matching is not None:
                self._raiseFailure('"{}" does not match "{}"'.format(
                         self.expected_regex.pattern, str(first_matching)))
            if self.obj_name:
                self._raiseFailure("{} not triggered by {}".format(exc_name,
                                                                   self.obj_name))
            else:
                self._raiseFailure("{} not triggered".format(exc_name))

    class _OrderedChainMap(collections.ChainMap):
        def __iter__(self):
            seen = set()
            for mapping in self.maps:
                for k in mapping:
                    if k not in seen:
                        seen.add(k)
                        yield k

    class TestCase(object):
        """A class whose instances are single test cases.

        By default, the test code itself should be placed in a method named
        'runTest'.

        If the fixture may be used for many test cases, create as
        many test methods as are needed. When instantiating such a TestCase
        subclass, specify in the constructor arguments the name of the test method
        that the instance is to execute.

        Test authors should subclass TestCase for their own tests. Construction
        and deconstruction of the test's environment ('fixture') can be
        implemented by overriding the 'setUp' and 'tearDown' methods respectively.

        If it is necessary to override the __init__ method, the base class
        __init__ method must always be called. It is important that subclasses
        should not change the signature of their __init__ method, since instances
        of the classes are instantiated automatically by parts of the framework
        in order to be run.

        When subclassing TestCase, you can set these attributes:
        * failureException: determines which exception will be raised when
            the instance's assertion methods fail; test methods raising this
            exception will be deemed to have 'failed' rather than 'errored'.
        * longMessage: determines whether long messages (including repr of
            objects used in assert methods) will be printed on failure in *addition*
            to any explicit message passed.
        * maxDiff: sets the maximum length of a diff in failure messages
            by assert methods using difflib. It is looked up as an instance
            attribute so can be configured by individual tests if required.
        """

        failureException = AssertionError

        longMessage = True

        maxDiff = 80*8

        # If a string is longer than _diffThreshold, use normal comparison instead
        # of difflib.  See #11763.
        _diffThreshold = 2**16

        def __init_subclass__(cls, *args, **kwargs):
            # Attribute used by TestSuite for classSetUp
            cls._classSetupFailed = False
            cls._class_cleanups = []
            super().__init_subclass__(*args, **kwargs)

        def __init__(self, methodName='runTest'):
            """Create an instance of the class that will use the named test
               method when executed. Raises a ValueError if the instance does
               not have a method with the specified name.
            """
            self._testMethodName = methodName
            self._outcome = None
            self._testMethodDoc = 'No test'
            try:
                testMethod = getattr(self, methodName)
            except AttributeError:
                if methodName != 'runTest':
                    # we allow instantiation with no explicit method name
                    # but not an *incorrect* or missing method name
                    raise ValueError("no such test method in %s: %s" %
                          (self.__class__, methodName))
            else:
                self._testMethodDoc = testMethod.__doc__
            self._cleanups = []
            self._subtest = None

            # Map types to custom assertEqual functions that will compare
            # instances of said type in more detail to generate a more useful
            # error message.
            self._type_equality_funcs = {}
            self.addTypeEqualityFunc(dict, 'assertDictEqual')
            self.addTypeEqualityFunc(list, 'assertListEqual')
            self.addTypeEqualityFunc(tuple, 'assertTupleEqual')
            self.addTypeEqualityFunc(set, 'assertSetEqual')
            self.addTypeEqualityFunc(frozenset, 'assertSetEqual')
            self.addTypeEqualityFunc(str, 'assertMultiLineEqual')

        def addTypeEqualityFunc(self, typeobj, function):
            """Add a type specific assertEqual style function to compare a type.

            This method is for use by TestCase subclasses that need to register
            their own type equality functions to provide nicer error messages.

            Args:
                typeobj: The data type to call this function on when both values
                        are of the same type in assertEqual().
                function: The callable taking two arguments and an optional
                        msg= argument that raises self.failureException with a
                        useful error message when the two arguments are not equal.
            """
            self._type_equality_funcs[typeobj] = function

        def addCleanup(self, function, /, *args, **kwargs):
            """Add a function, with arguments, to be called when the test is
            completed. Functions added are called on a LIFO basis and are
            called after tearDown on test failure or success.

            Cleanup items are called even if setUp fails (unlike tearDown)."""
            self._cleanups.append((function, args, kwargs))

        def enterContext(self, cm):
            """Enters the supplied context manager.

            If successful, also adds its __exit__ method as a cleanup
            function and returns the result of the __enter__ method.
            """
            return _enter_context(cm, self.addCleanup)

        @classmethod
        def addClassCleanup(cls, function, /, *args, **kwargs):
            """Same as addCleanup, except the cleanup items are called even if
            setUpClass fails (unlike tearDownClass)."""
            cls._class_cleanups.append((function, args, kwargs))

        @classmethod
        def enterClassContext(cls, cm):
            """Same as enterContext, but class-wide."""
            return _enter_context(cm, cls.addClassCleanup)

        def setUp(self):
            "Hook method for setting up the test fixture before exercising it."
            pass

        def tearDown(self):
            "Hook method for deconstructing the test fixture after testing it."
            pass

        @classmethod
        def setUpClass(cls):
            "Hook method for setting up class fixture before running tests in the class."

        @classmethod
        def tearDownClass(cls):
            "Hook method for deconstructing the class fixture after running all tests in the class."

        def countTestCases(self):
            return 1

        def defaultTestResult(self):
            return result.TestResult()

        def shortDescription(self):
            """Returns a one-line description of the test, or None if no
            description has been provided.

            The default implementation of this method returns the first line of
            the specified test method's docstring.
            """
            doc = self._testMethodDoc
            return doc.strip().split("\n")[0].strip() if doc else None

        def id(self):
            return "%s.%s" % (strclass(self.__class__), self._testMethodName)

        def __eq__(self, other):
            if type(self) is not type(other):
                return NotImplemented

            return self._testMethodName == other._testMethodName

        def __hash__(self):
            return hash((type(self), self._testMethodName))

        def __str__(self):
            return "%s (%s.%s)" % (self._testMethodName, strclass(self.__class__), self._testMethodName)

        def __repr__(self):
            return "<%s testMethod=%s>" % \
                   (strclass(self.__class__), self._testMethodName)

        @contextlib.contextmanager
        def subTest(self, msg=_subtest_msg_sentinel, **params):
            """Return a context manager that will return the enclosed block
            of code in a subtest identified by the optional message and
            keyword parameters.  A failure in the subtest marks the test
            case as failed but resumes execution at the end of the enclosed
            block, allowing further test code to be executed.
            """
            if self._outcome is None or not self._outcome.result_supports_subtests:
                yield
                return
            parent = self._subtest
            if parent is None:
                params_map = _OrderedChainMap(params)
            else:
                params_map = parent.params.new_child(params)
            self._subtest = _SubTest(self, msg, params_map)
            try:
                with self._outcome.testPartExecutor(self._subtest, subTest=True):
                    yield
                if not self._outcome.success:
                    result = self._outcome.result
                    if result is not None and result.failfast:
                        raise _ShouldStop
                elif self._outcome.expectedFailure:
                    # If the test is expecting a failure, we really want to
                    # stop now and register the expected failure.
                    raise _ShouldStop
            finally:
                self._subtest = parent

        def _addExpectedFailure(self, result, exc_info):
            try:
                addExpectedFailure = result.addExpectedFailure
            except AttributeError:
                warnings.warn("TestResult has no addExpectedFailure method, reporting as passes",
                              RuntimeWarning)
                result.addSuccess(self)
            else:
                addExpectedFailure(self, exc_info)

        def _addUnexpectedSuccess(self, result):
            try:
                addUnexpectedSuccess = result.addUnexpectedSuccess
            except AttributeError:
                warnings.warn("TestResult has no addUnexpectedSuccess method, reporting as failure",
                              RuntimeWarning)
                # We need to pass an actual exception and traceback to addFailure,
                # otherwise the legacy result can choke.
                try:
                    raise _UnexpectedSuccess from None
                except _UnexpectedSuccess:
                    result.addFailure(self, sys.exc_info())
            else:
                addUnexpectedSuccess(self)

        def _addDuration(self, result, elapsed):
            try:
                addDuration = result.addDuration
            except AttributeError:
                warnings.warn("TestResult has no addDuration method",
                              RuntimeWarning)
            else:
                addDuration(self, elapsed)

        def _callSetUp(self):
            self.setUp()

        def _callTestMethod(self, method):
            if method() is not None:
                warnings.warn(f'It is deprecated to return a value that is not None from a '
                              f'test case ({method})', DeprecationWarning, stacklevel=3)

        def _callTearDown(self):
            self.tearDown()

        def _callCleanup(self, function, /, *args, **kwargs):
            function(*args, **kwargs)

        def run(self, result=None):
            if result is None:
                result = self.defaultTestResult()
                startTestRun = getattr(result, 'startTestRun', None)
                stopTestRun = getattr(result, 'stopTestRun', None)
                if startTestRun is not None:
                    startTestRun()
            else:
                stopTestRun = None

            result.startTest(self)
            try:
                testMethod = getattr(self, self._testMethodName)
                if (getattr(self.__class__, "__unittest_skip__", False) or
                    getattr(testMethod, "__unittest_skip__", False)):
                    # If the class or method was skipped.
                    skip_why = (getattr(self.__class__, '__unittest_skip_why__', '')
                                or getattr(testMethod, '__unittest_skip_why__', ''))
                    _addSkip(result, self, skip_why)
                    return result

                expecting_failure = (
                    getattr(self, "__unittest_expecting_failure__", False) or
                    getattr(testMethod, "__unittest_expecting_failure__", False)
                )
                outcome = _Outcome(result)
                start_time = time.perf_counter()
                try:
                    self._outcome = outcome

                    with outcome.testPartExecutor(self):
                        self._callSetUp()
                    if outcome.success:
                        outcome.expecting_failure = expecting_failure
                        with outcome.testPartExecutor(self):
                            self._callTestMethod(testMethod)
                        outcome.expecting_failure = False
                        with outcome.testPartExecutor(self):
                            self._callTearDown()
                    self.doCleanups()
                    self._addDuration(result, (time.perf_counter() - start_time))

                    if outcome.success:
                        if expecting_failure:
                            if outcome.expectedFailure:
                                self._addExpectedFailure(result, outcome.expectedFailure)
                            else:
                                self._addUnexpectedSuccess(result)
                        else:
                            result.addSuccess(self)
                    return result
                finally:
                    # explicitly break reference cycle:
                    # outcome.expectedFailure -> frame -> outcome -> outcome.expectedFailure
                    outcome.expectedFailure = None
                    outcome = None

                    # clear the outcome, no more needed
                    self._outcome = None

            finally:
                result.stopTest(self)
                if stopTestRun is not None:
                    stopTestRun()

        def doCleanups(self):
            """Execute all cleanup functions. Normally called for you after
            tearDown."""
            outcome = self._outcome or _Outcome()
            while self._cleanups:
                function, args, kwargs = self._cleanups.pop()
                with outcome.testPartExecutor(self):
                    self._callCleanup(function, *args, **kwargs)

            # return this for backwards compatibility
            # even though we no longer use it internally
            return outcome.success

        @classmethod
        def doClassCleanups(cls):
            """Execute all class cleanup functions. Normally called for you after
            tearDownClass."""
            cls.tearDown_exceptions = []
            while cls._class_cleanups:
                function, args, kwargs = cls._class_cleanups.pop()
                try:
                    function(*args, **kwargs)
                except Exception:
                    cls.tearDown_exceptions.append(sys.exc_info())

        def __call__(self, *args, **kwds):
            return self.run(*args, **kwds)

        def debug(self):
            """Run the test without collecting errors in a TestResult"""
            testMethod = getattr(self, self._testMethodName)
            if (getattr(self.__class__, "__unittest_skip__", False) or
                getattr(testMethod, "__unittest_skip__", False)):
                # If the class or method was skipped.
                skip_why = (getattr(self.__class__, '__unittest_skip_why__', '')
                            or getattr(testMethod, '__unittest_skip_why__', ''))
                raise SkipTest(skip_why)

            self._callSetUp()
            self._callTestMethod(testMethod)
            self._callTearDown()
            while self._cleanups:
                function, args, kwargs = self._cleanups.pop()
                self._callCleanup(function, *args, **kwargs)

        def skipTest(self, reason):
            """Skip this test."""
            raise SkipTest(reason)

        def fail(self, msg=None):
            """Fail immediately, with the given message."""
            raise self.failureException(msg)

        def assertFalse(self, expr, msg=None):
            """Check that the expression is false."""
            if expr:
                msg = self._formatMessage(msg, "%s is not false" % safe_repr(expr))
                raise self.failureException(msg)

        def assertTrue(self, expr, msg=None):
            """Check that the expression is true."""
            if not expr:
                msg = self._formatMessage(msg, "%s is not true" % safe_repr(expr))
                raise self.failureException(msg)

        def _formatMessage(self, msg, standardMsg):
            """Honour the longMessage attribute when generating failure messages.
            If longMessage is False this means:
            * Use only an explicit message if it is provided
            * Otherwise use the standard message for the assert

            If longMessage is True:
            * Use the standard message
            * If an explicit message is provided, plus ' : ' and the explicit message
            """
            if not self.longMessage:
                return msg or standardMsg
            if msg is None:
                return standardMsg
            try:
                # don't switch to '{}' formatting in Python 2.X
                # it changes the way unicode input is handled
                return '%s : %s' % (standardMsg, msg)
            except UnicodeDecodeError:
                return  '%s : %s' % (safe_repr(standardMsg), safe_repr(msg))

        def assertRaises(self, expected_exception, *args, **kwargs):
            """Fail unless an exception of class expected_exception is raised
               by the callable when invoked with specified positional and
               keyword arguments. If a different type of exception is
               raised, it will not be caught, and the test case will be
               deemed to have suffered an error, exactly as for an
               unexpected exception.

               If called with the callable and arguments omitted, will return a
               context object used like this::

                    with self.assertRaises(SomeException):
                        do_something()

               An optional keyword argument 'msg' can be provided when assertRaises
               is used as a context object.

               The context manager keeps a reference to the exception as
               the 'exception' attribute. This allows you to inspect the
               exception after the assertion::

                   with self.assertRaises(SomeException) as cm:
                       do_something()
                   the_exception = cm.exception
                   self.assertEqual(the_exception.error_code, 3)
            """
            context = _AssertRaisesContext(expected_exception, self)
            try:
                return context.handle('assertRaises', args, kwargs)
            finally:
                # bpo-23890: manually break a reference cycle
                context = None

        def assertWarns(self, expected_warning, *args, **kwargs):
            """Fail unless a warning of class warnClass is triggered
               by the callable when invoked with specified positional and
               keyword arguments.  If a different type of warning is
               triggered, it will not be handled: depending on the other
               warning filtering rules in effect, it might be silenced, printed
               out, or raised as an exception.

               If called with the callable and arguments omitted, will return a
               context object used like this::

                    with self.assertWarns(SomeWarning):
                        do_something()

               An optional keyword argument 'msg' can be provided when assertWarns
               is used as a context object.

               The context manager keeps a reference to the first matching
               warning as the 'warning' attribute; similarly, the 'filename'
               and 'lineno' attributes give you information about the line
               of Python code from which the warning was triggered.
               This allows you to inspect the warning after the assertion::

                   with self.assertWarns(SomeWarning) as cm:
                       do_something()
                   the_warning = cm.warning
                   self.assertEqual(the_warning.some_attribute, 147)
            """
            context = _AssertWarnsContext(expected_warning, self)
            return context.handle('assertWarns', args, kwargs)

        def assertLogs(self, logger=None, level=None):
            """Fail unless a log message of level *level* or higher is emitted
            on *logger_name* or its children.  If omitted, *level* defaults to
            INFO and *logger* defaults to the root logger.

            This method must be used as a context manager, and will yield
            a recording object with two attributes: `output` and `records`.
            At the end of the context manager, the `output` attribute will
            be a list of the matching formatted log messages and the
            `records` attribute will be a list of the corresponding LogRecord
            objects.

            Example::

                with self.assertLogs('foo', level='INFO') as cm:
                    logging.getLogger('foo').info('first message')
                    logging.getLogger('foo.bar').error('second message')
                self.assertEqual(cm.output, ['INFO:foo:first message',
                                             'ERROR:foo.bar:second message'])
            """
            # Lazy import to avoid importing logging if it is not needed.
            from ._log import _AssertLogsContext
            return _AssertLogsContext(self, logger, level, no_logs=False)

        def assertNoLogs(self, logger=None, level=None):
            """ Fail unless no log messages of level *level* or higher are emitted
            on *logger_name* or its children.

            This method must be used as a context manager.
            """
            from ._log import _AssertLogsContext
            return _AssertLogsContext(self, logger, level, no_logs=True)

        def _getAssertEqualityFunc(self, first, second):
            """Get a detailed comparison function for the types of the two args.

            Returns: A callable accepting (first, second, msg=None) that will
            raise a failure exception if first != second with a useful human
            readable error message for those types.
            """
            #
            # NOTE(gregory.p.smith): I considered isinstance(first, type(second))
            # and vice versa.  I opted for the conservative approach in case
            # subclasses are not intended to be compared in detail to their super
            # class instances using a type equality func.  This means testing
            # subtypes won't automagically use the detailed comparison.  Callers
            # should use their type specific assertSpamEqual method to compare
            # subclasses if the detailed comparison is desired and appropriate.
            # See the discussion in http://bugs.python.org/issue2578.
            #
            if type(first) is type(second):
                asserter = self._type_equality_funcs.get(type(first))
                if asserter is not None:
                    if isinstance(asserter, str):
                        asserter = getattr(self, asserter)
                    return asserter

            return self._baseAssertEqual

        def _baseAssertEqual(self, first, second, msg=None):
            """The default assertEqual implementation, not type specific."""
            if not first == second:
                standardMsg = '%s != %s' % _common_shorten_repr(first, second)
                msg = self._formatMessage(msg, standardMsg)
                raise self.failureException(msg)

        def assertEqual(self, first, second, msg=None):
            """Fail if the two objects are unequal as determined by the '=='
               operator.
            """
            assertion_func = self._getAssertEqualityFunc(first, second)
            assertion_func(first, second, msg=msg)

        def assertNotEqual(self, first, second, msg=None):
            """Fail if the two objects are equal as determined by the '!='
               operator.
            """
            if not first != second:
                msg = self._formatMessage(msg, '%s == %s' % (safe_repr(first),
                                                              safe_repr(second)))
                raise self.failureException(msg)

        def assertAlmostEqual(self, first, second, places=None, msg=None,
                              delta=None):
            """Fail if the two objects are unequal as determined by their
               difference rounded to the given number of decimal places
               (default 7) and comparing to zero, or by comparing that the
               difference between the two objects 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 objects compare equal then they will automatically
               compare almost equal.
            """
            if first == second:
                # shortcut
                return
            if delta is not None and places is not None:
                raise TypeError("specify delta or places not both")

            diff = abs(first - second)
            if delta is not None:
                if diff <= delta:
                    return

                standardMsg = '%s != %s within %s delta (%s difference)' % (
                    safe_repr(first),
                    safe_repr(second),
                    safe_repr(delta),
                    safe_repr(diff))
            else:
                if places is None:
                    places = 7

                if round(diff, places) == 0:
                    return

                standardMsg = '%s != %s within %r places (%s difference)' % (
                    safe_repr(first),
                    safe_repr(second),
                    places,
                    safe_repr(diff))
            msg = self._formatMessage(msg, standardMsg)
            raise self.failureException(msg)

        def assertNotAlmostEqual(self, first, second, places=None, msg=None,
                                 delta=None):
            """Fail if the two objects are equal as determined by their
               difference rounded to the given number of decimal places
               (default 7) and comparing to zero, or by comparing that the
               difference between the two objects is less than the given delta.

               Note that decimal places (from zero) are usually not the same
               as significant digits (measured from the most significant digit).

               Objects that are equal automatically fail.
            """
            if delta is not None and places is not None:
                raise TypeError("specify delta or places not both")
            diff = abs(first - second)
            if delta is not None:
                if not (first == second) and diff > delta:
                    return
                standardMsg = '%s == %s within %s delta (%s difference)' % (
                    safe_repr(first),
                    safe_repr(second),
                    safe_repr(delta),
                    safe_repr(diff))
            else:
                if places is None:
                    places = 7
                if not (first == second) and round(diff, places) != 0:
                    return
                standardMsg = '%s == %s within %r places' % (safe_repr(first),
                                                             safe_repr(second),
                                                             places)

            msg = self._formatMessage(msg, standardMsg)
            raise self.failureException(msg)

        def assertSequenceEqual(self, seq1, seq2, msg=None, seq_type=None):
            """An equality assertion for ordered sequences (like lists and tuples).

            For the purposes of this function, a valid ordered sequence type is one
            which can be indexed, has a length, and has an equality operator.

            Args:
                seq1: The first sequence to compare.
                seq2: The second sequence to compare.
                seq_type: The expected datatype of the sequences, or None if no
                        datatype should be enforced.
                msg: Optional message to use on failure instead of a list of
                        differences.
            """
            if seq_type is not None:
                seq_type_name = seq_type.__name__
                if not isinstance(seq1, seq_type):
                    raise self.failureException('First sequence is not a %s: %s'
                                            % (seq_type_name, safe_repr(seq1)))
                if not isinstance(seq2, seq_type):
                    raise self.failureException('Second sequence is not a %s: %s'
                                            % (seq_type_name, safe_repr(seq2)))
            else:
                seq_type_name = "sequence"

            differing = None
            try:
                len1 = len(seq1)
            except (TypeError, NotImplementedError):
                differing = 'First %s has no length.    Non-sequence?' % (
                        seq_type_name)

            if differing is None:
                try:
                    len2 = len(seq2)
                except (TypeError, NotImplementedError):
                    differing = 'Second %s has no length.    Non-sequence?' % (
                            seq_type_name)

            if differing is None:
                if seq1 == seq2:
                    return

                differing = '%ss differ: %s != %s\n' % (
                        (seq_type_name.capitalize(),) +
                        _common_shorten_repr(seq1, seq2))

                for i in range(min(len1, len2)):
                    try:
                        item1 = seq1[i]
                    except (TypeError, IndexError, NotImplementedError):
                        differing += ('\nUnable to index element %d of first %s\n' %
                                     (i, seq_type_name))
                        break

                    try:
                        item2 = seq2[i]
                    except (TypeError, IndexError, NotImplementedError):
                        differing += ('\nUnable to index element %d of second %s\n' %
                                     (i, seq_type_name))
                        break

                    if item1 != item2:
                        differing += ('\nFirst differing element %d:\n%s\n%s\n' %
                                     ((i,) + _common_shorten_repr(item1, item2)))
                        break
                else:
                    if (len1 == len2 and seq_type is None and
                        type(seq1) != type(seq2)):
                        # The sequences are the same, but have differing types.
                        return

                if len1 > len2:
                    differing += ('\nFirst %s contains %d additional '
                                 'elements.\n' % (seq_type_name, len1 - len2))
                    try:
                        differing += ('First extra element %d:\n%s\n' %
                                      (len2, safe_repr(seq1[len2])))
                    except (TypeError, IndexError, NotImplementedError):
                        differing += ('Unable to index element %d '
                                      'of first %s\n' % (len2, seq_type_name))
                elif len1 < len2:
                    differing += ('\nSecond %s contains %d additional '
                                 'elements.\n' % (seq_type_name, len2 - len1))
                    try:
                        differing += ('First extra element %d:\n%s\n' %
                                      (len1, safe_repr(seq2[len1])))
                    except (TypeError, IndexError, NotImplementedError):
                        differing += ('Unable to index element %d '
                                      'of second %s\n' % (len1, seq_type_name))
            standardMsg = differing
            diffMsg = '\n' + '\n'.join(
                difflib.ndiff(pprint.pformat(seq1).splitlines(),
                              pprint.pformat(seq2).splitlines()))

            standardMsg = self._truncateMessage(standardMsg, diffMsg)
            msg = self._formatMessage(msg, standardMsg)
            self.fail(msg)

        def _truncateMessage(self, message, diff):
            max_diff = self.maxDiff
            if max_diff is None or len(diff) <= max_diff:
                return message + diff
            return message + (DIFF_OMITTED % len(diff))

        def assertListEqual(self, list1, list2, msg=None):
            """A list-specific equality assertion.

            Args:
                list1: The first list to compare.
                list2: The second list to compare.
                msg: Optional message to use on failure instead of a list of
                        differences.

            """
            self.assertSequenceEqual(list1, list2, msg, seq_type=list)

        def assertTupleEqual(self, tuple1, tuple2, msg=None):
            """A tuple-specific equality assertion.

            Args:
                tuple1: The first tuple to compare.
                tuple2: The second tuple to compare.
                msg: Optional message to use on failure instead of a list of
                        differences.
            """
            self.assertSequenceEqual(tuple1, tuple2, msg, seq_type=tuple)

        def assertSetEqual(self, set1, set2, msg=None):
            """A set-specific equality assertion.

            Args:
                set1: The first set to compare.
                set2: The second set to compare.
                msg: Optional message to use on failure instead of a list of
                        differences.

            assertSetEqual uses ducktyping to support different types of sets, and
            is optimized for sets specifically (parameters must support a
            difference method).
            """
            try:
                difference1 = set1.difference(set2)
            except TypeError as e:
                self.fail('invalid type when attempting set difference: %s' % e)
            except AttributeError as e:
                self.fail('first argument does not support set difference: %s' % e)

            try:
                difference2 = set2.difference(set1)
            except TypeError as e:
                self.fail('invalid type when attempting set difference: %s' % e)
            except AttributeError as e:
                self.fail('second argument does not support set difference: %s' % e)

            if not (difference1 or difference2):
                return

            lines = []
            if difference1:
                lines.append('Items in the first set but not the second:')
                for item in difference1:
                    lines.append(repr(item))
            if difference2:
                lines.append('Items in the second set but not the first:')
                for item in difference2:
                    lines.append(repr(item))

            standardMsg = '\n'.join(lines)
            self.fail(self._formatMessage(msg, standardMsg))

        def assertIn(self, member, container, msg=None):
            """Just like self.assertTrue(a in b), but with a nicer default message."""
            if member not in container:
                standardMsg = '%s not found in %s' % (safe_repr(member),
                                                      safe_repr(container))
                self.fail(self._formatMessage(msg, standardMsg))

        def assertNotIn(self, member, container, msg=None):
            """Just like self.assertTrue(a not in b), but with a nicer default message."""
            if member in container:
                standardMsg = '%s unexpectedly found in %s' % (safe_repr(member),
                                                            safe_repr(container))
                self.fail(self._formatMessage(msg, standardMsg))

        def assertIs(self, expr1, expr2, msg=None):
            """Just like self.assertTrue(a is b), but with a nicer default message."""
            if expr1 is not expr2:
                standardMsg = '%s is not %s' % (safe_repr(expr1),
                                                 safe_repr(expr2))
                self.fail(self._formatMessage(msg, standardMsg))

        def assertIsNot(self, expr1, expr2, msg=None):
            """Just like self.assertTrue(a is not b), but with a nicer default message."""
            if expr1 is expr2:
                standardMsg = 'unexpectedly identical: %s' % (safe_repr(expr1),)
                self.fail(self._formatMessage(msg, standardMsg))

        def assertDictEqual(self, d1, d2, msg=None):
            self.assertIsInstance(d1, dict, 'First argument is not a dictionary')
            self.assertIsInstance(d2, dict, 'Second argument is not a dictionary')

            if d1 != d2:
                standardMsg = '%s != %s' % _common_shorten_repr(d1, d2)
                diff = ('\n' + '\n'.join(difflib.ndiff(
                               pprint.pformat(d1).splitlines(),
                               pprint.pformat(d2).splitlines())))
                standardMsg = self._truncateMessage(standardMsg, diff)
                self.fail(self._formatMessage(msg, standardMsg))

        def assertCountEqual(self, first, second, msg=None):
            """Asserts that two iterables have the same elements, the same number of
            times, without regard to order.

                self.assertEqual(Counter(list(first)),
                                 Counter(list(second)))

             Example:
                - [0, 1, 1] and [1, 0, 1] compare equal.
                - [0, 0, 1] and [0, 1] compare unequal.

            """
            first_seq, second_seq = list(first), list(second)
            try:
                first = collections.Counter(first_seq)
                second = collections.Counter(second_seq)
            except TypeError:
                # Handle case with unhashable elements
                differences = _count_diff_all_purpose(first_seq, second_seq)
            else:
                if first == second:
                    return
                differences = _count_diff_hashable(first_seq, second_seq)

            if differences:
                standardMsg = 'Element counts were not equal:\n'
                lines = ['First has %d, Second has %d:  %r' % diff for diff in differences]
                diffMsg = '\n'.join(lines)
                standardMsg = self._truncateMessage(standardMsg, diffMsg)
                msg = self._formatMessage(msg, standardMsg)
                self.fail(msg)

        def assertMultiLineEqual(self, first, second, msg=None):
            """Assert that two multi-line strings are equal."""
            self.assertIsInstance(first, str, "First argument is not a string")
            self.assertIsInstance(second, str, "Second argument is not a string")

            if first != second:
                # Don't use difflib if the strings are too long
                if (len(first) > self._diffThreshold or
                    len(second) > self._diffThreshold):
                    self._baseAssertEqual(first, second, msg)

                # Append \n to both strings if either is missing the \n.
                # This allows the final ndiff to show the \n difference. The
                # exception here is if the string is empty, in which case no
                # \n should be added
                first_presplit = first
                second_presplit = second
                if first and second:
                    if first[-1] != '\n' or second[-1] != '\n':
                        first_presplit += '\n'
                        second_presplit += '\n'
                elif second and second[-1] != '\n':
                    second_presplit += '\n'
                elif first and first[-1] != '\n':
                    first_presplit += '\n'

                firstlines = first_presplit.splitlines(keepends=True)
                secondlines = second_presplit.splitlines(keepends=True)

                # Generate the message and diff, then raise the exception
                standardMsg = '%s != %s' % _common_shorten_repr(first, second)
                diff = '\n' + ''.join(difflib.ndiff(firstlines, secondlines))
                standardMsg = self._truncateMessage(standardMsg, diff)
                self.fail(self._formatMessage(msg, standardMsg))

        def assertLess(self, a, b, msg=None):
            """Just like self.assertTrue(a < b), but with a nicer default message."""
            if not a < b:
                standardMsg = '%s not less than %s' % (safe_repr(a), safe_repr(b))
                self.fail(self._formatMessage(msg, standardMsg))

        def assertLessEqual(self, a, b, msg=None):
            """Just like self.assertTrue(a <= b), but with a nicer default message."""
            if not a <= b:
                standardMsg = '%s not less than or equal to %s' % (safe_repr(a), safe_repr(b))
                self.fail(self._formatMessage(msg, standardMsg))

        def assertGreater(self, a, b, msg=None):
            """Just like self.assertTrue(a > b), but with a nicer default message."""
            if not a > b:
                standardMsg = '%s not greater than %s' % (safe_repr(a), safe_repr(b))
                self.fail(self._formatMessage(msg, standardMsg))

        def assertGreaterEqual(self, a, b, msg=None):
            """Just like self.assertTrue(a >= b), but with a nicer default message."""
            if not a >= b:
                standardMsg = '%s not greater than or equal to %s' % (safe_repr(a), safe_repr(b))
                self.fail(self._formatMessage(msg, standardMsg))

        def assertIsNone(self, obj, msg=None):
            """Same as self.assertTrue(obj is None), with a nicer default message."""
            if obj is not None:
                standardMsg = '%s is not None' % (safe_repr(obj),)
                self.fail(self._formatMessage(msg, standardMsg))

        def assertIsNotNone(self, obj, msg=None):
            """Included for symmetry with assertIsNone."""
            if obj is None:
                standardMsg = 'unexpectedly None'
                self.fail(self._formatMessage(msg, standardMsg))

        def assertIsInstance(self, obj, cls, msg=None):
            """Same as self.assertTrue(isinstance(obj, cls)), with a nicer
            default message."""
            if not isinstance(obj, cls):
                standardMsg = '%s is not an instance of %r' % (safe_repr(obj), cls)
                self.fail(self._formatMessage(msg, standardMsg))

        def assertNotIsInstance(self, obj, cls, msg=None):
            """Included for symmetry with assertIsInstance."""
            if isinstance(obj, cls):
                standardMsg = '%s is an instance of %r' % (safe_repr(obj), cls)
                self.fail(self._formatMessage(msg, standardMsg))

        def assertRaisesRegex(self, expected_exception, expected_regex,
                              *args, **kwargs):
            """Asserts that the message in a raised exception matches a regex.

            Args:
                expected_exception: Exception class expected to be raised.
                expected_regex: Regex (re.Pattern object or string) expected
                        to be found in error message.
                args: Function to be called and extra positional args.
                kwargs: Extra kwargs.
                msg: Optional message used in case of failure. Can only be used
                        when assertRaisesRegex is used as a context manager.
            """
            context = _AssertRaisesContext(expected_exception, self, expected_regex)
            return context.handle('assertRaisesRegex', args, kwargs)

        def assertWarnsRegex(self, expected_warning, expected_regex,
                             *args, **kwargs):
            """Asserts that the message in a triggered warning matches a regexp.
            Basic functioning is similar to assertWarns() with the addition
            that only warnings whose messages also match the regular expression
            are considered successful matches.

            Args:
                expected_warning: Warning class expected to be triggered.
                expected_regex: Regex (re.Pattern object or string) expected
                        to be found in error message.
                args: Function to be called and extra positional args.
                kwargs: Extra kwargs.
                msg: Optional message used in case of failure. Can only be used
                        when assertWarnsRegex is used as a context manager.
            """
            context = _AssertWarnsContext(expected_warning, self, expected_regex)
            return context.handle('assertWarnsRegex', args, kwargs)

        def assertRegex(self, text, expected_regex, msg=None):
            """Fail the test unless the text matches the regular expression."""
            if isinstance(expected_regex, (str, bytes)):
                assert expected_regex, "expected_regex must not be empty."
                expected_regex = re.compile(expected_regex)
            if not expected_regex.search(text):
                standardMsg = "Regex didn't match: %r not found in %r" % (
                    expected_regex.pattern, text)
                # _formatMessage ensures the longMessage option is respected
                msg = self._formatMessage(msg, standardMsg)
                raise self.failureException(msg)

        def assertNotRegex(self, text, unexpected_regex, msg=None):
            """Fail the test if the text matches the regular expression."""
            if isinstance(unexpected_regex, (str, bytes)):
                unexpected_regex = re.compile(unexpected_regex)
            match = unexpected_regex.search(text)
            if match:
                standardMsg = 'Regex matched: %r matches %r in %r' % (
                    text[match.start() : match.end()],
                    unexpected_regex.pattern,
                    text)
                # _formatMessage ensures the longMessage option is respected
                msg = self._formatMessage(msg, standardMsg)
                raise self.failureException(msg)

    class FunctionTestCase(TestCase):
        """A test case that wraps a test function.

        This is useful for slipping pre-existing test functions into the
        unittest framework. Optionally, set-up and tidy-up functions can be
        supplied. As with TestCase, the tidy-up ('tearDown') function will
        always be called if the set-up ('setUp') function ran successfully.
        """

        def __init__(self, testFunc, setUp=None, tearDown=None, description=None):
            super(FunctionTestCase, self).__init__()
            self._setUpFunc = setUp
            self._tearDownFunc = tearDown
            self._testFunc = testFunc
            self._description = description

        def setUp(self):
            if self._setUpFunc is not None:
                self._setUpFunc()

        def tearDown(self):
            if self._tearDownFunc is not None:
                self._tearDownFunc()

        def runTest(self):
            self._testFunc()

        def id(self):
            return self._testFunc.__name__

        def __eq__(self, other):
            if not isinstance(other, self.__class__):
                return NotImplemented

            return self._setUpFunc == other._setUpFunc and \
                   self._tearDownFunc == other._tearDownFunc and \
                   self._testFunc == other._testFunc and \
                   self._description == other._description

        def __hash__(self):
            return hash((type(self), self._setUpFunc, self._tearDownFunc,
                         self._testFunc, self._description))

        def __str__(self):
            return "%s (%s)" % (strclass(self.__class__),
                                self._testFunc.__name__)

        def __repr__(self):
            return "<%s tec=%s>" % (strclass(self.__class__),
                                         self._testFunc)

        def shortDescription(self):
            if self._description is not None:
                return self._description
            doc = self._testFunc.__doc__
            return doc and doc.split("\n")[0].strip() or None

    class _SubTest(TestCase):

        def __init__(self, test_case, message, params):
            super().__init__()
            self._message = message
            self.test_case = test_case
            self.params = params
            self.failureException = test_case.failureException

        def runTest(self):
            raise NotImplementedError("subtests cannot be run directly")

        def _subDescription(self):
            parts = []
            if self._message is not _subtest_msg_sentinel:
                parts.append("[{}]".format(self._message))
            if self.params:
                params_desc = ', '.join(
                    "{}={!r}".format(k, v)
                    for (k, v) in self.params.items())
                parts.append("({})".format(params_desc))
            return " ".join(parts) or '(<subtest>)'

        def id(self):
            return "{} {}".format(self.test_case.id(), self._subDescription())

        def shortDescription(self):
            """Returns a one-line description of the subtest, or None if no
            description has been provided.
            """
            return self.test_case.shortDescription()

        def __str__(self):
            return "{} {}".format(self.test_case, self._subDescription())