唯快不破：mock源码剖析

       有时，你需要为单元测试的初始设置准备一些“其他”的代码资源。但这些资源兴许会不可用，不稳定，或者是使用起来太笨重。你可以试着找一些其他的资源替代；或者你可以通过创建一个被称为mock的东西来模拟它。Mocks能够让我们模拟那些在单元测试中不可用或太笨重的资源。总之就是mock可以屏蔽一些我们不需要关系的细节。

mock.py

# mock.py# Test tools for mocking and patching.# E-mail: fuzzyman AT voidspace DOT org DOT uk## mock 1.0.1# http://www.voidspace.org.uk/python/mock/## Copyright (c) 2007-2013, Michael Foord & the mock team# All rights reserved.## Redistribution and use in source and binary forms, with or without# modification, are permitted provided that the following conditions are# met:##     * Redistributions of source code must retain the above copyright#       notice, this list of conditions and the following disclaimer.##     * Redistributions in binary form must reproduce the above#       copyright notice, this list of conditions and the following#       disclaimer in the documentation and/or other materials provided#       with the distribution.## THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.from __future__ import absolute_import__all__ = (    '__version__',    'version_info',    'Mock',    'MagicMock',    'patch',    'sentinel',    'DEFAULT',    'ANY',    'call',    'create_autospec',    'FILTER_DIR',    'CallableMixin',    'NonCallableMock',    'NonCallableMagicMock',    'mock_open',    'PropertyMock',)from functools import partialimport inspectimport pprintimport systry:    import builtinsexcept ImportError:    import __builtin__ as builtinsfrom types import ModuleTypeimport sixfrom six import wrapsfrom pbr.version import VersionInfo_v = VersionInfo('mock').semantic_version()__version__ = _v.release_string()version_info = _v.version_tuple()import mocktry:    inspectsignature = inspect.signatureexcept AttributeError:    import funcsigs    inspectsignature = funcsigs.signature# TODO: use six.try:    unicodeexcept NameError:    # Python 3    basestring = unicode = strtry:    longexcept NameError:    # Python 3    long = inttry:    BaseExceptionexcept NameError:    # Python 2.4 compatibility    BaseException = Exceptionif six.PY2:    # Python 2's next() can't handle a non-iterator with a __next__ method.    _next = next    def next(obj, _next=_next):        if getattr(obj, '__next__', None):            return obj.__next__()        return _next(obj)    del _next_builtins = set(name for name in dir(builtins) if not name.startswith('_'))BaseExceptions = (BaseException,)if 'java' in sys.platform:    # jython    import java    BaseExceptions = (BaseException, java.lang.Throwable)try:    _isidentifier = str.isidentifierexcept AttributeError:    # Python 2.X    import keyword    import re    regex = re.compile(r'^[a-z_][a-z0-9_]*$', re.I)    def _isidentifier(string):        if string in keyword.kwlist:            return False        return regex.match(string)self = 'im_self'builtin = '__builtin__'if six.PY3:    self = '__self__'    builtin = 'builtins'# NOTE: This FILTER_DIR is not used. The binding in mock.FILTER_DIR is.FILTER_DIR = True# Workaround for Python issue #12370# Without this, the __class__ properties wouldn't be set correctly_safe_super = superdef _is_instance_mock(obj):    # can't use isinstance on Mock objects because they override __class__    # The base class for all mocks is NonCallableMock    return issubclass(type(obj), NonCallableMock)def _is_exception(obj):    return (        isinstance(obj, BaseExceptions) or        isinstance(obj, ClassTypes) and issubclass(obj, BaseExceptions)    )class _slotted(object):    __slots__ = ['a']DescriptorTypes = (    type(_slotted.a),    property,)def _get_signature_object(func, as_instance, eat_self):    """    获取任何可调用对象的签名对象.    Given an arbitrary, possibly callable object, try to create a suitable    signature object.    Return a (reduced func, signature) tuple, or None.    """    if isinstance(func, ClassTypes) and not as_instance:        # 如果是类型，就返回__init__方法签名        # If it's a type and should be modelled as a type, use __init__.        try:            func = func.__init__        except AttributeError:            return None        # Skip the `self` argument in __init__        # 跳过self参数        eat_self = True    elif not isinstance(func, FunctionTypes):        # 不是方法的其他对象都返回__call__方法签名        # If we really want to model an instance of the passed type,        # __call__ should be looked up, not __init__.        try:            func = func.__call__        except AttributeError:            return None    if eat_self:        # 跳过self        sig_func = partial(func, None)    else:        sig_func = func    try:        return func, inspectsignature(sig_func)    except ValueError:        # Certain callable types are not supported by inspect.signature()        return Nonedef _check_signature(func, mock, skipfirst, instance=False):    # 为mock对象设置方法签名检查方法    sig = _get_signature_object(func, instance, skipfirst)    if sig is None:        return    func, sig = sig    def checksig(_mock_self, *args, **kwargs):        # 执行函数签名检查        sig.bind(*args, **kwargs)    # 拷贝方法其他元信息    _copy_func_details(func, checksig)    type(mock)._mock_check_sig = checksigdef _copy_func_details(func, funcopy):    u"""拷贝方法元信息"""    funcopy.__name__ = func.__name__    funcopy.__doc__ = func.__doc__    try:        funcopy.__text_signature__ = func.__text_signature__    except AttributeError:        pass    # we explicitly don't copy func.__dict__ into this copy as it would    # expose original attributes that should be mocked    try:        funcopy.__module__ = func.__module__    except AttributeError:        pass    try:        funcopy.__defaults__ = func.__defaults__    except AttributeError:        pass    try:        funcopy.__kwdefaults__ = func.__kwdefaults__    except AttributeError:        pass    if six.PY2:        funcopy.func_defaults = func.func_defaults        returndef _callable(obj):    if isinstance(obj, ClassTypes):        return True    if getattr(obj, '__call__', None) is not None:        return True    return Falsedef _is_list(obj):    # checks for list or tuples    # XXXX badly named!    return type(obj) in (list, tuple)def _instance_callable(obj):    """Given an object, return True if the object is callable.    For classes, return True if instances would be callable."""    if not isinstance(obj, ClassTypes):        # already an instance        return getattr(obj, '__call__', None) is not None    if six.PY3:        # *could* be broken by a class overriding __mro__ or __dict__ via        # a metaclass        for base in (obj,) + obj.__mro__:            if base.__dict__.get('__call__') is not None:                return True    else:        klass = obj        # uses __bases__ instead of __mro__ so that we work with old style classes        if klass.__dict__.get('__call__') is not None:            return True        for base in klass.__bases__:            if _instance_callable(base):                return True    return Falsedef _set_signature(mock, original, instance=False):    # 封装mock对象为带签名检查的函数对象    # creates a function with signature (*args, **kwargs) that delegates to a    # mock. It still does signature checking by calling a lambda with the same    # signature as the original.    if not _callable(original):        return    skipfirst = isinstance(original, ClassTypes)    result = _get_signature_object(original, instance, skipfirst)    if result is None:        return    func, sig = result    def checksig(*args, **kwargs):        sig.bind(*args, **kwargs)    _copy_func_details(func, checksig)    name = original.__name__    if not _isidentifier(name):        # 与关键字重名        name = 'funcopy'    context = {'_checksig_': checksig, 'mock': mock}    src = """def %s(*args, **kwargs):    _checksig_(*args, **kwargs)    return mock(*args, **kwargs)""" % name    six.exec_(src, context)    funcopy = context[name]    _setup_func(funcopy, mock)    return funcopydef _setup_func(funcopy, mock):    funcopy.mock = mock    # can't use isinstance with mocks    if not _is_instance_mock(mock):        return    def assert_called_with(*args, **kwargs):        return mock.assert_called_with(*args, **kwargs)    def assert_called_once_with(*args, **kwargs):        return mock.assert_called_once_with(*args, **kwargs)    def assert_has_calls(*args, **kwargs):        return mock.assert_has_calls(*args, **kwargs)    def assert_any_call(*args, **kwargs):        return mock.assert_any_call(*args, **kwargs)    def reset_mock():        funcopy.method_calls = _CallList()        funcopy.mock_calls = _CallList()        mock.reset_mock()        ret = funcopy.return_value        if _is_instance_mock(ret) and not ret is mock:            ret.reset_mock()    funcopy.called = False    funcopy.call_count = 0    funcopy.call_args = None    funcopy.call_args_list = _CallList()    funcopy.method_calls = _CallList()    funcopy.mock_calls = _CallList()    funcopy.return_value = mock.return_value    funcopy.side_effect = mock.side_effect    funcopy._mock_children = mock._mock_children    funcopy.assert_called_with = assert_called_with    funcopy.assert_called_once_with = assert_called_once_with    funcopy.assert_has_calls = assert_has_calls    funcopy.assert_any_call = assert_any_call    funcopy.reset_mock = reset_mock    mock._mock_delegate = funcopydef _is_magic(name):    return '__%s__' % name[2:-2] == nameclass _SentinelObject(object):    """哨兵对象"""    "A unique, named, sentinel object."    def __init__(self, name):        self.name = name    def __repr__(self):        return 'sentinel.%s' % self.nameclass _Sentinel(object):    """Access attributes to return a named object, usable as a sentinel."""    def __init__(self):        self._sentinels = {}    def __getattr__(self, name):        """通过访问属性返回一个命名的哨兵对象"""        if name == '__bases__':            # Without this help(unittest.mock) raises an exception            raise AttributeError        return self._sentinels.setdefault(name, _SentinelObject(name))sentinel = _Sentinel()DEFAULT = sentinel.DEFAULT_missing = sentinel.MISSING_deleted = sentinel.DELETEDclass OldStyleClass:    passClassType = type(OldStyleClass)def _copy(value):    if type(value) in (dict, list, tuple, set):        return type(value)(value)    return valueClassTypes = (type,)if six.PY2:    ClassTypes = (type, ClassType)_allowed_names = set((    'return_value', '_mock_return_value', 'side_effect',    '_mock_side_effect', '_mock_parent', '_mock_new_parent',    '_mock_name', '_mock_new_name'))def _delegating_property(name):    _allowed_names.add(name)    _the_name = '_mock_' + name    def _get(self, name=name, _the_name=_the_name):        sig = self._mock_delegate        if sig is None:            return getattr(self, _the_name)        return getattr(sig, name)    def _set(self, value, name=name, _the_name=_the_name):        sig = self._mock_delegate        if sig is None:            self.__dict__[_the_name] = value        else:            setattr(sig, name, value)    return property(_get, _set)class _CallList(list):    def __contains__(self, value):        if not isinstance(value, list):            return list.__contains__(self, value)        len_value = len(value)        len_self = len(self)        if len_value > len_self:            return False        for i in range(0, len_self - len_value + 1):            sub_list = self[i:i+len_value]            if sub_list == value:                return True        return False    def __repr__(self):        return pprint.pformat(list(self))def _check_and_set_parent(parent, value, name, new_name):    if not _is_instance_mock(value):        return False    if ((value._mock_name or value._mock_new_name) or        (value._mock_parent is not None) or        (value._mock_new_parent is not None)):        return False    _parent = parent    while _parent is not None:        # setting a mock (value) as a child or return value of itself        # should not modify the mock        if _parent is value:            return False        _parent = _parent._mock_new_parent    if new_name:        value._mock_new_parent = parent        value._mock_new_name = new_name    if name:        value._mock_parent = parent        value._mock_name = name    return True# Internal class to identify if we wrapped an iterator object or not.class _MockIter(object):    def __init__(self, obj):        self.obj = iter(obj)    def __iter__(self):        return self    def __next__(self):        return next(self.obj)class Base(object):    _mock_return_value = DEFAULT    _mock_side_effect = None    def __init__(self, *args, **kwargs):        passclass NonCallableMock(Base):    u"""不可以直接调用的mock类."""    """A non-callable version of `Mock`"""    def __new__(cls, *args, **kw):        u"""以name创建一个类，并返回新实例.所以mock对象直接不会相互影响."""        # every instance has its own class        # so we can create magic methods on the        # class without stomping on other mocks        new = type(cls.__name__, (cls,), {'__doc__': cls.__doc__})        instance = object.__new__(new)        return instance    def __init__(            self, spec=None, wraps=None, name=None, spec_set=None,            parent=None, _spec_state=None, _new_name='', _new_parent=None,            _spec_as_instance=False, _eat_self=None, unsafe=False, **kwargs        ):        if _new_parent is None:            _new_parent = parent        __dict__ = self.__dict__        __dict__['_mock_parent'] = parent        __dict__['_mock_name'] = name        __dict__['_mock_new_name'] = _new_name        __dict__['_mock_new_parent'] = _new_parent        if spec_set is not None:            spec = spec_set            spec_set = True        if _eat_self is None:            _eat_self = parent is not None        # 添加spec mock方法        self._mock_add_spec(spec, spec_set, _spec_as_instance, _eat_self)        __dict__['_mock_children'] = {}        __dict__['_mock_wraps'] = wraps        __dict__['_mock_delegate'] = None        __dict__['_mock_called'] = False        __dict__['_mock_call_args'] = None        __dict__['_mock_call_count'] = 0        __dict__['_mock_call_args_list'] = _CallList()        __dict__['_mock_mock_calls'] = _CallList()        __dict__['method_calls'] = _CallList()        __dict__['_mock_unsafe'] = unsafe        if kwargs:            # 配置mock对象            self.configure_mock(**kwargs)        _safe_super(NonCallableMock, self).__init__(            spec, wraps, name, spec_set, parent,            _spec_state        )    def attach_mock(self, mock, attribute):        """        Attach a mock as an attribute of this one, replacing its name and        parent. Calls to the attached mock will be recorded in the        `method_calls` and `mock_calls` attributes of this one."""        mock._mock_parent = None        mock._mock_new_parent = None        mock._mock_name = ''        mock._mock_new_name = None        setattr(self, attribute, mock)    def mock_add_spec(self, spec, spec_set=False):        """Add a spec to a mock. `spec` can either be an object or a        list of strings. Only attributes on the `spec` can be fetched as        attributes from the mock.        If `spec_set` is True then only attributes on the spec can be set."""        self._mock_add_spec(spec, spec_set)    def _mock_add_spec(self, spec, spec_set, _spec_as_instance=False,                       _eat_self=False):        u"""添加spec mock方法."""        _spec_class = None        _spec_signature = None        if spec is not None and not _is_list(spec):            if isinstance(spec, ClassTypes):                _spec_class = spec            else:                _spec_class = _get_class(spec)            # spec类的签名            res = _get_signature_object(spec,                                        _spec_as_instance, _eat_self)            _spec_signature = res and res[1]            spec = dir(spec)        __dict__ = self.__dict__        __dict__['_spec_class'] = _spec_class        __dict__['_spec_set'] = spec_set        __dict__['_spec_signature'] = _spec_signature        __dict__['_mock_methods'] = spec    def __get_return_value(self):        ret = self._mock_return_value        if self._mock_delegate is not None:            ret = self._mock_delegate.return_value        if ret is DEFAULT:            ret = self._get_child_mock(                _new_parent=self, _new_name='()'            )            self.return_value = ret        return ret    def __set_return_value(self, value):        if self._mock_delegate is not None:            self._mock_delegate.return_value = value        else:            self._mock_return_value = value            _check_and_set_parent(self, value, None, '()')    __return_value_doc = "The value to be returned when the mock is called."    return_value = property(__get_return_value, __set_return_value,                            __return_value_doc)    @property    def __class__(self):        if self._spec_class is None:            return type(self)        return self._spec_class    called = _delegating_property('called')    call_count = _delegating_property('call_count')    call_args = _delegating_property('call_args')    call_args_list = _delegating_property('call_args_list')    mock_calls = _delegating_property('mock_calls')    def __get_side_effect(self):        delegated = self._mock_delegate        if delegated is None:            return self._mock_side_effect        sf = delegated.side_effect        if (sf is not None and not callable(sf)                and not isinstance(sf, _MockIter) and not _is_exception(sf)):            sf = _MockIter(sf)            delegated.side_effect = sf        return sf    def __set_side_effect(self, value):        value = _try_iter(value)        delegated = self._mock_delegate        if delegated is None:            self._mock_side_effect = value        else:            delegated.side_effect = value    side_effect = property(__get_side_effect, __set_side_effect)    def reset_mock(self, visited=None):        "Restore the mock object to its initial state."        if visited is None:            visited = []        if id(self) in visited:            return        visited.append(id(self))        self.called = False        self.call_args = None        self.call_count = 0        self.mock_calls = _CallList()        self.call_args_list = _CallList()        self.method_calls = _CallList()        for child in self._mock_children.values():            if isinstance(child, _SpecState):                continue            child.reset_mock(visited)        ret = self._mock_return_value        if _is_instance_mock(ret) and ret is not self:            ret.reset_mock(visited)    def configure_mock(self, **kwargs):        """Set attributes on the mock through keyword arguments.        Attributes plus return values and side effects can be set on child        mocks using standard dot notation and unpacking a dictionary in the        method call:        >>> attrs = {'method.return_value': 3, 'other.side_effect': KeyError}        >>> mock.configure_mock(**attrs)"""        for arg, val in sorted(kwargs.items(),                               # we sort on the number of dots so that                               # attributes are set before we set attributes on                               # attributes                               key=lambda entry: entry[0].count('.')):            args = arg.split('.')            final = args.pop()            obj = self            for entry in args:                obj = getattr(obj, entry)            setattr(obj, final, val)    def __getattr__(self, name):        u"""获取mock对象属性，不存在的创建mock对象"""        if name in ('_mock_methods', '_mock_unsafe'):            raise AttributeError(name)        elif self._mock_methods is not None:            if name not in self._mock_methods or name in _all_magics:                raise AttributeError("Mock object has no attribute %r" % name)        elif _is_magic(name):            raise AttributeError(name)        if not self._mock_unsafe:            if name.startswith(('assert', 'assret')):                raise AttributeError(name)        result = self._mock_children.get(name)        if result is _deleted:            raise AttributeError(name)        elif result is None:            wraps = None            if self._mock_wraps is not None:                # XXXX should we get the attribute without triggering code                # execution?                wraps = getattr(self._mock_wraps, name)            result = self._get_child_mock(                parent=self, name=name, wraps=wraps, _new_name=name,                _new_parent=self            )            self._mock_children[name]  = result        elif isinstance(result, _SpecState):            result = create_autospec(                result.spec, result.spec_set, result.instance,                result.parent, result.name            )            self._mock_children[name]  = result        return result    def __repr__(self):        _name_list = [self._mock_new_name]        _parent = self._mock_new_parent        last = self        dot = '.'        if _name_list == ['()']:            dot = ''        seen = set()        while _parent is not None:            last = _parent            _name_list.append(_parent._mock_new_name + dot)            dot = '.'            if _parent._mock_new_name == '()':                dot = ''            _parent = _parent._mock_new_parent            # use ids here so as not to call __hash__ on the mocks            if id(_parent) in seen:                break            seen.add(id(_parent))        _name_list = list(reversed(_name_list))        _first = last._mock_name or 'mock'        if len(_name_list) > 1:            if _name_list[1] not in ('()', '().'):                _first += '.'        _name_list[0] = _first        name = ''.join(_name_list)        name_string = ''        if name not in ('mock', 'mock.'):            name_string = ' name=%r' % name        spec_string = ''        if self._spec_class is not None:            spec_string = ' spec=%r'            if self._spec_set:                spec_string = ' spec_set=%r'            spec_string = spec_string % self._spec_class.__name__        return "<%s%s%s id='%s'>" % (            type(self).__name__,            name_string,            spec_string,            id(self)        )    def __dir__(self):        """Filter the output of `dir(mock)` to only useful members."""        if not mock.FILTER_DIR and getattr(object, '__dir__', None):            # object.__dir__ is not in 2.7            return object.__dir__(self)        extras = self._mock_methods or []        from_type = dir(type(self))        from_dict = list(self.__dict__)        if mock.FILTER_DIR:            # object.__dir__ is not in 2.7            from_type = [e for e in from_type if not e.startswith('_')]            from_dict = [e for e in from_dict if not e.startswith('_') or                         _is_magic(e)]        return sorted(set(extras + from_type + from_dict +                          list(self._mock_children)))    def __setattr__(self, name, value):        u"""设置mock对象属性，如果传递spec_set会进行检查"""        if name in _allowed_names:            # property setters go through here            return object.__setattr__(self, name, value)        elif (self._spec_set and self._mock_methods is not None and            #设置spec_set为True不能设置不存在的属性            name not in self._mock_methods and            name not in self.__dict__):            # 不能设置非mock方法和不存在属性            raise AttributeError("Mock object has no attribute '%s'" % name)        elif name in _unsupported_magics:            msg = 'Attempting to set unsupported magic method %r.' % name            raise AttributeError(msg)        elif name in _all_magics:            if self._mock_methods is not None and name not in self._mock_methods:                raise AttributeError("Mock object has no attribute '%s'" % name)            if not _is_instance_mock(value):                setattr(type(self), name, _get_method(name, value))                original = value                value = lambda *args, **kw: original(self, *args, **kw)            else:                # only set _new_name and not name so that mock_calls is tracked                # but not method calls                _check_and_set_parent(self, value, None, name)                setattr(type(self), name, value)                self._mock_children[name] = value        elif name == '__class__':            self._spec_class = value            return        else:            if _check_and_set_parent(self, value, name, name):                self._mock_children[name] = value        return object.__setattr__(self, name, value)    def __delattr__(self, name):        if name in _all_magics and name in type(self).__dict__:            delattr(type(self), name)            if name not in self.__dict__:                # for magic methods that are still MagicProxy objects and                # not set on the instance itself                return        if name in self.__dict__:            object.__delattr__(self, name)        obj = self._mock_children.get(name, _missing)        if obj is _deleted:            raise AttributeError(name)        if obj is not _missing:            del self._mock_children[name]        self._mock_children[name] = _deleted    def _format_mock_call_signature(self, args, kwargs):        name = self._mock_name or 'mock'        return _format_call_signature(name, args, kwargs)    def _format_mock_failure_message(self, args, kwargs):        message = 'Expected call: %s\nActual call: %s'        expected_string = self._format_mock_call_signature(args, kwargs)        call_args = self.call_args        if len(call_args) == 3:            call_args = call_args[1:]        actual_string = self._format_mock_call_signature(*call_args)        return message % (expected_string, actual_string)    def _call_matcher(self, _call):        """        Given a call (or simply a (args, kwargs) tuple), return a        comparison key suitable for matching with other calls.        This is a best effort method which relies on the spec's signature,        if available, or falls back on the arguments themselves.        """        sig = self._spec_signature        if sig is not None:            if len(_call) == 2:                name = ''                args, kwargs = _call            else:                name, args, kwargs = _call            try:                return name, sig.bind(*args, **kwargs)            except TypeError as e:                e.__traceback__ = None                return e        else:            return _call    def assert_not_called(_mock_self):        """assert that the mock was never called.        """        self = _mock_self        if self.call_count != 0:            msg = ("Expected '%s' to not have been called. Called %s times." %                   (self._mock_name or 'mock', self.call_count))            raise AssertionError(msg)    def assert_called(_mock_self):        """assert that the mock was called at least once        """        self = _mock_self        if self.call_count == 0:            msg = ("Expected '%s' to have been called." %                   self._mock_name or 'mock')            raise AssertionError(msg)    def assert_called_once(_mock_self):        """assert that the mock was called only once.        """        self = _mock_self        if not self.call_count == 1:            msg = ("Expected '%s' to have been called once. Called %s times." %                   (self._mock_name or 'mock', self.call_count))            raise AssertionError(msg)    def assert_called_with(_mock_self, *args, **kwargs):        """assert that the mock was called with the specified arguments.        Raises an AssertionError if the args and keyword args passed in are        different to the last call to the mock."""        self = _mock_self        if self.call_args is None:            expected = self._format_mock_call_signature(args, kwargs)            raise AssertionError('Expected call: %s\nNot called' % (expected,))        def _error_message(cause):            msg = self._format_mock_failure_message(args, kwargs)            if six.PY2 and cause is not None:                # Tack on some diagnostics for Python without __cause__                msg = '%s\n%s' % (msg, str(cause))            return msg        expected = self._call_matcher((args, kwargs))        actual = self._call_matcher(self.call_args)        if expected != actual:            cause = expected if isinstance(expected, Exception) else None            six.raise_from(AssertionError(_error_message(cause)), cause)    def assert_called_once_with(_mock_self, *args, **kwargs):        """assert that the mock was called exactly once and with the specified        arguments."""        self = _mock_self        if not self.call_count == 1:            msg = ("Expected '%s' to be called once. Called %s times." %                   (self._mock_name or 'mock', self.call_count))            raise AssertionError(msg)        return self.assert_called_with(*args, **kwargs)    def assert_has_calls(self, calls, any_order=False):        """assert the mock has been called with the specified calls.        The `mock_calls` list is checked for the calls.        If `any_order` is False (the default) then the calls must be        sequential. There can be extra calls before or after the        specified calls.        If `any_order` is True then the calls can be in any order, but        they must all appear in `mock_calls`."""        expected = [self._call_matcher(c) for c in calls]        cause = expected if isinstance(expected, Exception) else None        all_calls = _CallList(self._call_matcher(c) for c in self.mock_calls)        if not any_order:            if expected not in all_calls:                six.raise_from(AssertionError(                    'Calls not found.\nExpected: %r\n'                    'Actual: %r' % (_CallList(calls), self.mock_calls)                ), cause)            return        all_calls = list(all_calls)        not_found = []        for kall in expected:            try:                all_calls.remove(kall)            except ValueError:                not_found.append(kall)        if not_found:            six.raise_from(AssertionError(                '%r not all found in call list' % (tuple(not_found),)            ), cause)    def assert_any_call(self, *args, **kwargs):        """assert the mock has been called with the specified arguments.        The assert passes if the mock has *ever* been called, unlike        `assert_called_with` and `assert_called_once_with` that only pass if        the call is the most recent one."""        expected = self._call_matcher((args, kwargs))        actual = [self._call_matcher(c) for c in self.call_args_list]        if expected not in actual:            cause = expected if isinstance(expected, Exception) else None            expected_string = self._format_mock_call_signature(args, kwargs)            six.raise_from(AssertionError(                '%s call not found' % expected_string            ), cause)    def _get_child_mock(self, **kw):        """Create the child mocks for attributes and return value.        By default child mocks will be the same type as the parent.        Subclasses of Mock may want to override this to customize the way        child mocks are made.        For non-callable mocks the callable variant will be used (rather than        any custom subclass)."""        _type = type(self)        if not issubclass(_type, CallableMixin):            if issubclass(_type, NonCallableMagicMock):                klass = MagicMock            elif issubclass(_type, NonCallableMock) :                klass = Mock        else:            klass = _type.__mro__[1]        return klass(**kw)def _try_iter(obj):    if obj is None:        return obj    if _is_exception(obj):        return obj    if _callable(obj):        return obj    try:        return iter(obj)    except TypeError:        # XXXX backwards compatibility        # but this will blow up on first call - so maybe we should fail early?        return objclass CallableMixin(Base):    u"""可以调用的mock类.    负责调用逻辑封装，添加签名检查    负责调用统计工作    """    def __init__(self, spec=None, side_effect=None, return_value=DEFAULT,                 wraps=None, name=None, spec_set=None, parent=None,                 _spec_state=None, _new_name='', _new_parent=None, **kwargs):        self.__dict__['_mock_return_value'] = return_value        _safe_super(CallableMixin, self).__init__(            spec, wraps, name, spec_set, parent,            _spec_state, _new_name, _new_parent, **kwargs        )        self.side_effect = side_effect    def _mock_check_sig(self, *args, **kwargs):        # stub method that can be replaced with one with a specific signature        pass    def __call__(_mock_self, *args, **kwargs):        # can't use self in-case a function / method we are mocking uses self        # in the signature        # 函数签名检查        _mock_self._mock_check_sig(*args, **kwargs)        return _mock_self._mock_call(*args, **kwargs)    def _mock_call(_mock_self, *args, **kwargs):        # mock调用统计        self = _mock_self        self.called = True        self.call_count += 1        _new_name = self._mock_new_name        _new_parent = self._mock_new_parent        _call = _Call((args, kwargs), two=True)        self.call_args = _call        self.call_args_list.append(_call)        self.mock_calls.append(_Call(('', args, kwargs)))        seen = set()        skip_next_dot = _new_name == '()'        do_method_calls = self._mock_parent is not None        name = self._mock_name        while _new_parent is not None:            this_mock_call = _Call((_new_name, args, kwargs))            if _new_parent._mock_new_name:                dot = '.'                if skip_next_dot:                    dot = ''                skip_next_dot = False                if _new_parent._mock_new_name == '()':                    skip_next_dot = True                _new_name = _new_parent._mock_new_name + dot + _new_name            if do_method_calls:                if _new_name == name:                    this_method_call = this_mock_call                else:                    this_method_call = _Call((name, args, kwargs))                _new_parent.method_calls.append(this_method_call)                do_method_calls = _new_parent._mock_parent is not None                if do_method_calls:                    name = _new_parent._mock_name + '.' + name            _new_parent.mock_calls.append(this_mock_call)            _new_parent = _new_parent._mock_new_parent            # use ids here so as not to call __hash__ on the mocks            _new_parent_id = id(_new_parent)            if _new_parent_id in seen:                break            seen.add(_new_parent_id)        # 返回值默认是DEFAULT        ret_val = DEFAULT        effect = self.side_effect        if effect is not None:            # side_effect抛出异常            if _is_exception(effect):                raise effect            if not _callable(effect):                # 如果side_effect是列表则依次取列表值                result = next(effect)                if _is_exception(result):                    raise result                if result is DEFAULT:                    result = self.return_value                return result            # 如果side_effect可调用则调用取返回值            ret_val = effect(*args, **kwargs)        if (self._mock_wraps is not None and             self._mock_return_value is DEFAULT):            return self._mock_wraps(*args, **kwargs)        if ret_val is DEFAULT:            # 如果side_effect返回值为DEFAULT则返回return_value            ret_val = self.return_value        return ret_valclass Mock(CallableMixin, NonCallableMock):    """    Create a new `Mock` object. `Mock` takes several optional arguments    that specify the behaviour of the Mock object:    * `spec`: This can be either a list of strings or an existing object (a      class or instance) that acts as the specification for the mock object. If      you pass in an object then a list of strings is formed by calling dir on      the object (excluding unsupported magic attributes and methods). Accessing      any attribute not in this list will raise an `AttributeError`.      If `spec` is an object (rather than a list of strings) then      `mock.__class__` returns the class of the spec object. This allows mocks      to pass `isinstance` tests.    * `spec_set`: A stricter variant of `spec`. If used, attempting to *set*      or get an attribute on the mock that isn't on the object passed as      `spec_set` will raise an `AttributeError`.    * `side_effect`: A function to be called whenever the Mock is called. See      the `side_effect` attribute. Useful for raising exceptions or      dynamically changing return values. The function is called with the same      arguments as the mock, and unless it returns `DEFAULT`, the return      value of this function is used as the return value.      Alternatively `side_effect` can be an exception class or instance. In      this case the exception will be raised when the mock is called.      If `side_effect` is an iterable then each call to the mock will return      the next value from the iterable. If any of the members of the iterable      are exceptions they will be raised instead of returned.    * `return_value`: The value returned when the mock is called. By default      this is a new Mock (created on first access). See the      `return_value` attribute.    * `wraps`: Item for the mock object to wrap. If `wraps` is not None then      calling the Mock will pass the call through to the wrapped object      (returning the real result). Attribute access on the mock will return a      Mock object that wraps the corresponding attribute of the wrapped object      (so attempting to access an attribute that doesn't exist will raise an      `AttributeError`).      If the mock has an explicit `return_value` set then calls are not passed      to the wrapped object and the `return_value` is returned instead.    * `name`: If the mock has a name then it will be used in the repr of the      mock. This can be useful for debugging. The name is propagated to child      mocks.    Mocks can also be called with arbitrary keyword arguments. These will be    used to set attributes on the mock after it is created.    """def _dot_lookup(thing, comp, import_path):    try:        return getattr(thing, comp)    except AttributeError:        # 对于phoenix.server.manager情况必须先import phoenix.server.manager        # 才能从phoenix.server模块中获取manager属性，否则会抛属性不存在异常        __import__(import_path)        return getattr(thing, comp)def _importer(target):    """执行实际导入工作的函数体"""    components = target.split('.')    import_path = components.pop(0)    thing = __import__(import_path)    for comp in components:        # 不能直接import，需采用层层递进的方式导入宿主对象        import_path += ".%s" % comp        thing = _dot_lookup(thing, comp, import_path)    return thingdef _is_started(patcher):    # XXXX horrible    return hasattr(patcher, 'is_local')class _patch(object):    """补丁对象"""    attribute_name = None    _active_patches = []    def __init__(            self, getter, attribute, new, spec, create,            spec_set, autospec, new_callable, kwargs        ):        if new_callable is not None:            if new is not DEFAULT:                # 不能同时指定new和new_callable                raise ValueError(                    "Cannot use 'new' and 'new_callable' together"                )            if autospec is not None:                # 不能同时指定autospec和new_callable                raise ValueError(                    "Cannot use 'autospec' and 'new_callable' together"                )        self.getter = getter        self.attribute = attribute        self.new = new        self.new_callable = new_callable        self.spec = spec        self.create = create        self.has_local = False        self.spec_set = spec_set        self.autospec = autospec        self.kwargs = kwargs        self.additional_patchers = []    def copy(self):        patcher = _patch(            self.getter, self.attribute, self.new, self.spec,            self.create, self.spec_set,            self.autospec, self.new_callable, self.kwargs        )        patcher.attribute_name = self.attribute_name        patcher.additional_patchers = [            p.copy() for p in self.additional_patchers        ]        return patcher    def __call__(self, func):        # __call__后于__init__后调用        if isinstance(func, ClassTypes):            # 装饰类            return self.decorate_class(func)        # 装饰方法        return self.decorate_callable(func)    def decorate_class(self, klass):        u"""装饰整个单元测试类."""        for attr in dir(klass):            if not attr.startswith(patch.TEST_PREFIX):                # 跳过非_test开头的方法                continue            attr_value = getattr(klass, attr)            if not hasattr(attr_value, "__call__"):                # 跳过非调用属性                continue            patcher = self.copy()            # 依次每个测试用例方法调用__call__            setattr(klass, attr, patcher(attr_value))        return klass    def decorate_callable(self, func):        u"""装饰单个单元测试方法.        Args:            func:被装饰的方法        """        if hasattr(func, 'patchings'):            # python装饰器从下往上解析，就近原则            # 当有多个装饰器作用时都添加的方法的patchings属性中            func.patchings.append(self)            return func        # wraps装饰器的作用时保存原方法的元信息        @wraps(func)        def patched(*args, **keywargs):            u"""被打补丁后的方法."""            # 补丁对象参数集合            extra_args = []            #已打好补丁集合            entered_patchers = []            exc_info = tuple()            try:                # 依次打补丁                for patching in patched.patchings:                    # 打补丁，并返回补丁对象                    arg = patching.__enter__()                    # 将已经打好的补丁添加到已打补丁集合中                    entered_patchers.append(patching)                    if patching.attribute_name is not None:                        keywargs.update(arg)                    elif patching.new is DEFAULT:                        # 没有指定补丁对象，就将当前已打好的补丁对象添加到参数                        # 集合中，并传递给所装饰的方法                        extra_args.append(arg)                # 将打好的补丁对象集合传递给方法                args += tuple(extra_args)                return func(*args, **keywargs)            except:                if (patching not in entered_patchers and                    _is_started(patching)):                    # 确保所有已打的补丁都会被解除，不残留                    # the patcher may have been started, but an exception                    # raised whilst entering one of its additional_patchers                    entered_patchers.append(patching)                # Pass the exception to __exit__                exc_info = sys.exc_info()                # re-raise the exception                raise            finally:                # 反向依次解除所有补丁，跟打补丁的顺序相反                for patching in reversed(entered_patchers):                    # 解除补丁                    patching.__exit__(*exc_info)        # 打第一个补丁创建patchings属性        patched.patchings = [self]        return patched    def get_original(self):        u"""获取打补丁前原始的对象."""        # 导入宿主对象        target = self.getter()        # 将被打补丁对象在宿主对象中的属性名称        name = self.attribute        original = DEFAULT        # 补丁对象是否在本地查找空间中        local = False        try:            # 从宿主对象中获取要打补丁的原始对象            original = target.__dict__[name]        except (AttributeError, KeyError):            original = getattr(target, name, DEFAULT)        else:            # 在本地查找空间中            local = True        if name in _builtins and isinstance(target, ModuleType):            # 要打补丁的对象在__builtin__内置模块中            self.create = True        if not self.create and original is DEFAULT:            # 即不在__builtin__模块中也不在本地中，属性不存在            raise AttributeError(                "%s does not have the attribute %r" % (target, name)            )        return original, local    def __enter__(self):        u"""Perform the patch.        打补丁的真正方法执行过程.        """        new, spec, spec_set = self.new, self.spec, self.spec_set        autospec, kwargs = self.autospec, self.kwargs        new_callable = self.new_callable        # 当方法实际执行的时候才正式导入宿主对象        self.target = self.getter()        # normalise False to None        if spec is False:            spec = None        if spec_set is False:            spec_set = None        if autospec is False:            autospec = None        if spec is not None and autospec is not None:            # spec和autospec参数不能同时指定            raise TypeError("Can't specify spec and autospec")        if ((spec is not None or autospec is not None) and            spec_set not in (True, None)):            # 当指定spec或autospec参数时，spec_set参数只能指定True值或不指定值            raise TypeError("Can't provide explicit spec_set *and* spec or autospec")        # 获取打补丁前原始的对象        original, local = self.get_original()        if new is DEFAULT and autospec is None:            inherit = False            # spec和spec_set参数处理细节            if spec is True:                # set spec to the object we are replacing                spec = original                if spec_set is True:                    spec_set = original                    spec = None            elif spec is not None:                if spec_set is True:                    spec_set = spec                    spec = None            elif spec_set is True:                spec_set = original            if spec is not None or spec_set is not None:                if original is DEFAULT:                    # __builtin__模块不支持spec、spec_set                    raise TypeError("Can't use 'spec' with create=True")                if isinstance(original, ClassTypes):                    # If we're patching out a class and there is a spec                    # 如果是类，子类要打补丁                    inherit = True            # 默认补丁对象类型是MagicMock            Klass = MagicMock            _kwargs = {}            if new_callable is not None:                # new_callable传递的情况，补丁对象就是new_callable返回值                Klass = new_callable            elif spec is not None or spec_set is not None:                this_spec = spec                if spec_set is not None:                    this_spec = spec_set                if _is_list(this_spec):                    not_callable = '__call__' not in this_spec                else:                    not_callable = not _callable(this_spec)                if not_callable:                    # spec规定补丁对象不能被调用                    Klass = NonCallableMagicMock            # 将spec、spec_set参数传递给补丁对象            if spec is not None:                _kwargs['spec'] = spec            if spec_set is not None:                _kwargs['spec_set'] = spec_set            # add a name to mocks            if (isinstance(Klass, type) and                issubclass(Klass, NonCallableMock) and self.attribute):                _kwargs['name'] = self.attribute            _kwargs.update(kwargs)            new = Klass(**_kwargs)            if inherit and _is_instance_mock(new):                # we can only tell if the instance should be callable if the                # spec is not a list                this_spec = spec                if spec_set is not None:                    this_spec = spec_set                if (not _is_list(this_spec) and not                    _instance_callable(this_spec)):                    Klass = NonCallableMagicMock                _kwargs.pop('name')                new.return_value = Klass(_new_parent=new, _new_name='()',                                         **_kwargs)        elif autospec is not None:            # autospec传递情况下会根据原始对象生成mock对象            # spec被忽略，new必须是DEFAULT，spec_set被作为bool值处理            # spec is ignored, new *must* be default, spec_set is treated            # as a boolean. Should we check spec is not None and that spec_set            # is a bool?            if new is not DEFAULT:                # 指定autospec时不能指定new                raise TypeError(                    "autospec creates the mock for you. Can't specify "                    "autospec and new."                )            if original is DEFAULT:                #__builtins__不支持autospec                raise TypeError("Can't use 'autospec' with create=True")            # 将spec_set转为bool类型            spec_set = bool(spec_set)            if autospec is True:                autospec = original            new = create_autospec(autospec, spec_set=spec_set,                                  _name=self.attribute, **kwargs)        elif kwargs:            # can't set keyword args when we aren't creating the mock            # XXXX If new is a Mock we could call new.configure_mock(**kwargs)            raise TypeError("Can't pass kwargs to a mock we aren't creating")        new_attr = new        self.temp_original = original        self.is_local = local        # 替换原先对象        setattr(self.target, self.attribute, new_attr)        if self.attribute_name is not None:            extra_args = {}            if self.new is DEFAULT:                extra_args[self.attribute_name] =  new            for patching in self.additional_patchers:                arg = patching.__enter__()                if patching.new is DEFAULT:                    extra_args.update(arg)            return extra_args        return new    def __exit__(self, *exc_info):        """Undo the patch."""        if not _is_started(self):            raise RuntimeError('stop called on unstarted patcher')        if self.is_local and self.temp_original is not DEFAULT:            setattr(self.target, self.attribute, self.temp_original)        else:            delattr(self.target, self.attribute)            if not self.create and (not hasattr(self.target, self.attribute) or                        self.attribute in ('__doc__', '__module__',                                           '__defaults__', '__annotations__',                                           '__kwdefaults__')):                # needed for proxy objects like django settings                setattr(self.target, self.attribute, self.temp_original)        del self.temp_original        del self.is_local        del self.target        for patcher in reversed(self.additional_patchers):            if _is_started(patcher):                patcher.__exit__(*exc_info)    def start(self):        """Activate a patch, returning any created mock."""        result = self.__enter__()        self._active_patches.append(self)        return result    def stop(self):        """Stop an active patch."""        try:            self._active_patches.remove(self)        except ValueError:            # If the patch hasn't been started this will fail            pass        return self.__exit__()def _get_target(target):    """    返回导入宿主对象的函数和被mock对象在宿主对象中属性名称    """    try:        # 如果target=phoenix.server.manager.Manager        # 那么拆分后target=phoenix.server.manager，attribute=Manager        target, attribute = target.rsplit('.', 1)    except (TypeError, ValueError):        # 像target=os情况会抛出异常        raise TypeError("Need a valid target to patch. You supplied: %r" %                        (target,))    # getter是python语法糖lambda生成的一个匿名函数    # 函数体就是 _importer(target)    getter = lambda: _importer(target)    return getter, attributedef _patch_object(        target, attribute, new=DEFAULT, spec=None,        create=False, spec_set=None, autospec=None,        new_callable=None, **kwargs    ):    """给对象的attribute打补丁"""    """    patch the named member (`attribute`) on an object (`target`) with a mock    object.    `patch.object` can be used as a decorator, class decorator or a context    manager. Arguments `new`, `spec`, `create`, `spec_set`,    `autospec` and `new_callable` have the same meaning as for `patch`. Like    `patch`, `patch.object` takes arbitrary keyword arguments for configuring    the mock object it creates.    When used as a class decorator `patch.object` honours `patch.TEST_PREFIX`    for choosing which methods to wrap.    """    getter = lambda: target    return _patch(        getter, attribute, new, spec, create,        spec_set, autospec, new_callable, kwargs    )def _patch_multiple(target, spec=None, create=False, spec_set=None,                    autospec=None, new_callable=None, **kwargs):    u"""一条patch代码打多个补丁"""    """Perform multiple patches in a single call. It takes the object to be    patched (either as an object or a string to fetch the object by importing)    and keyword arguments for the patches::        with patch.multiple(settings, FIRST_PATCH='one', SECOND_PATCH='two'):            ...    Use `DEFAULT` as the value if you want `patch.multiple` to create    mocks for you. In this case the created mocks are passed into a decorated    function by keyword, and a dictionary is returned when `patch.multiple` is    used as a context manager.    `patch.multiple` can be used as a decorator, class decorator or a context    manager. The arguments `spec`, `spec_set`, `create`,    `autospec` and `new_callable` have the same meaning as for `patch`. These    arguments will be applied to *all* patches done by `patch.multiple`.    When used as a class decorator `patch.multiple` honours `patch.TEST_PREFIX`    for choosing which methods to wrap.    """    if type(target) in (unicode, str):        getter = lambda: _importer(target)    else:        getter = lambda: target    if not kwargs:        raise ValueError(            'Must supply at least one keyword argument with patch.multiple'        )    # need to wrap in a list for python 3, where items is a view    items = list(kwargs.items())    attribute, new = items[0]    patcher = _patch(        getter, attribute, new, spec, create, spec_set,        autospec, new_callable, {}    )    patcher.attribute_name = attribute    for attribute, new in items[1:]:        this_patcher = _patch(            getter, attribute, new, spec, create, spec_set,            autospec, new_callable, {}        )        this_patcher.attribute_name = attribute        patcher.additional_patchers.append(this_patcher)    return patcherdef patch(        target, new=DEFAULT, spec=None, create=False,        spec_set=None, autospec=None, new_callable=None, **kwargs    ):    """    patch是单元测试用例中使用广泛的装饰器.    mock.patch即可用在测试用例方法上，也可以用在测试类上。可以看到patch接收多个    参数，分别是target、new、spec、create、spec_set、autospec、new_callable、    kwargs，下面解释下各个参数的作用：    target：可导入，需要替换的对象    new：如果忽略new参数，那么target就会被MagicMock对象替换，否则被new对象替换。    spec：可以是list、类、True，如果是list则新生成的mock对象只包含list中的属性    和方法，如果是类，则只包含类中的属性和方法，如果是True则包含原始对象中所有    的属性和方法。    spec_set：能传True或类，表示设置存在的属性。    create：指定为True，当要替换的属性不存在的时候，就创建该属性，危险！    autospec：指定为True，只包含原对象中的方法和属性，并会进行方法调用参数强校验    new_callable：可以指定其他类或可调用对象替换掉默认的MagicMock对象    kwargs：可以传递给MagicMock初始化方法或被装饰的方法    `patch` acts as a function decorator, class decorator or a context    manager. Inside the body of the function or with statement, the `target`    is patched with a `new` object. When the function/with statement exits    the patch is undone.    If `new` is omitted, then the target is replaced with a    `MagicMock`. If `patch` is used as a decorator and `new` is    omitted, the created mock is passed in as an extra argument to the    decorated function. If `patch` is used as a context manager the created    mock is returned by the context manager.    `target` should be a string in the form `'package.module.ClassName'`. The    `target` is imported and the specified object replaced with the `new`    object, so the `target` must be importable from the environment you are    calling `patch` from. The target is imported when the decorated function    is executed, not at decoration time.    The `spec` and `spec_set` keyword arguments are passed to the `MagicMock`    if patch is creating one for you.    In addition you can pass `spec=True` or `spec_set=True`, which causes    patch to pass in the object being mocked as the spec/spec_set object.    `new_callable` allows you to specify a different class, or callable object,    that will be called to create the `new` object. By default `MagicMock` is    used.    A more powerful form of `spec` is `autospec`. If you set `autospec=True`    then the mock will be created with a spec from the object being replaced.    All attributes of the mock will also have the spec of the corresponding    attribute of the object being replaced. Methods and functions being    mocked will have their arguments checked and will raise a `TypeError` if    they are called with the wrong signature. For mocks replacing a class,    their return value (the 'instance') will have the same spec as the class.    Instead of `autospec=True` you can pass `autospec=some_object` to use an    arbitrary object as the spec instead of the one being replaced.    By default `patch` will fail to replace attributes that don't exist. If    you pass in `create=True`, and the attribute doesn't exist, patch will    create the attribute for you when the patched function is called, and    delete it again afterwards. This is useful for writing tests against    attributes that your production code creates at runtime. It is off by    default because it can be dangerous. With it switched on you can write    passing tests against APIs that don't actually exist!    Patch can be used as a `TestCase` class decorator. It works by    decorating each test method in the class. This reduces the boilerplate    code when your test methods share a common patchings set. `patch` finds    tests by looking for method names that start with `patch.TEST_PREFIX`.    By default this is `test`, which matches the way `unittest` finds tests.    You can specify an alternative prefix by setting `patch.TEST_PREFIX`.    Patch can be used as a context manager, with the with statement. Here the    patching applies to the indented block after the with statement. If you    use "as" then the patched object will be bound to the name after the    "as"; very useful if `patch` is creating a mock object for you.    `patch` takes arbitrary keyword arguments. These will be passed to    the `Mock` (or `new_callable`) on construction.    `patch.dict(...)`, `patch.multiple(...)` and `patch.object(...)` are    available for alternate use-cases.    """    # 获取被mock对象的宿主对象，和被mock对象在宿主对象中的属性名称    # 注意这里的getter并不是对象，而是可以导入对象的一个函数，只有当被装饰方法    # 实际调用的时候才真正导入宿主对象    getter, attribute = _get_target(target)    return _patch(        getter, attribute, new, spec, create,        spec_set, autospec, new_callable, kwargs    )class _patch_dict(object):    """给dict或对象打补丁"""    """    Patch a dictionary, or dictionary like object, and restore the dictionary    to its original state after the test.    `in_dict` can be a dictionary or a mapping like container. If it is a    mapping then it must at least support getting, setting and deleting items    plus iterating over keys.    `in_dict` can also be a string specifying the name of the dictionary, which    will then be fetched by importing it.    `values` can be a dictionary of values to set in the dictionary. `values`    can also be an iterable of `(key, value)` pairs.    If `clear` is True then the dictionary will be cleared before the new    values are set.    `patch.dict` can also be called with arbitrary keyword arguments to set    values in the dictionary::        with patch.dict('sys.modules', mymodule=Mock(), other_module=Mock()):            ...    `patch.dict` can be used as a context manager, decorator or class    decorator. When used as a class decorator `patch.dict` honours    `patch.TEST_PREFIX` for choosing which methods to wrap.    """    def __init__(self, in_dict, values=(), clear=False, **kwargs):        if isinstance(in_dict, basestring):            in_dict = _importer(in_dict)        self.in_dict = in_dict        # support any argument supported by dict(...) constructor        self.values = dict(values)        self.values.update(kwargs)        self.clear = clear        self._original = None    def __call__(self, f):        if isinstance(f, ClassTypes):            return self.decorate_class(f)        @wraps(f)        def _inner(*args, **kw):            self._patch_dict()            try:                return f(*args, **kw)            finally:                self._unpatch_dict()        return _inner    def decorate_class(self, klass):        for attr in dir(klass):            attr_value = getattr(klass, attr)            if (attr.startswith(patch.TEST_PREFIX) and                 hasattr(attr_value, "__call__")):                decorator = _patch_dict(self.in_dict, self.values, self.clear)                decorated = decorator(attr_value)                setattr(klass, attr, decorated)        return klass    def __enter__(self):        """Patch the dict."""        self._patch_dict()    def _patch_dict(self):        values = self.values        in_dict = self.in_dict        clear = self.clear        try:            original = in_dict.copy()        except AttributeError:            # dict like object with no copy method            # must support iteration over keys            original = {}            for key in in_dict:                original[key] = in_dict[key]        # 把原始的先保存起来        self._original = original        if clear:            _clear_dict(in_dict)        try:            in_dict.update(values)        except AttributeError:            # dict like object with no update method            for key in values:                in_dict[key] = values[key]    def _unpatch_dict(self):        in_dict = self.in_dict        original = self._original        _clear_dict(in_dict)        try:            # 恢复原始值            in_dict.update(original)        except AttributeError:            for key in original:                in_dict[key] = original[key]    def __exit__(self, *args):        """Unpatch the dict."""        self._unpatch_dict()        return False    start = __enter__    stop = __exit__def _clear_dict(in_dict):    try:        in_dict.clear()    except AttributeError:        keys = list(in_dict)        for key in keys:            del in_dict[key]def _patch_stopall():    """取消所有补丁"""    """Stop all active patches. LIFO to unroll nested patches."""    for patch in reversed(_patch._active_patches):        patch.stop()patch.object = _patch_objectpatch.dict = _patch_dictpatch.multiple = _patch_multiplepatch.stopall = _patch_stopallpatch.TEST_PREFIX = 'test'magic_methods = (    "lt le gt ge eq ne "    "getitem setitem delitem "    "len contains iter "    "hash str sizeof "    "enter exit "    # we added divmod and rdivmod here instead of numerics    # because there is no idivmod    "divmod rdivmod neg pos abs invert "    "complex int float index "    "trunc floor ceil ")numerics = (    "add sub mul matmul div floordiv mod lshift rshift and xor or pow")if six.PY3:    numerics += ' truediv'inplace = ' '.join('i%s' % n for n in numerics.split())right = ' '.join('r%s' % n for n in numerics.split())extra = ''if six.PY3:    extra = 'bool next 'else:    extra = 'unicode long nonzero oct hex truediv rtruediv '# not including __prepare__, __instancecheck__, __subclasscheck__# (as they are metaclass methods)# __del__ is not supported at all as it causes problems if it exists_non_defaults = set((    '__cmp__', '__getslice__', '__setslice__', '__coerce__', # <3.x    '__get__', '__set__', '__delete__', '__reversed__', '__missing__',    '__reduce__', '__reduce_ex__', '__getinitargs__', '__getnewargs__',    '__getstate__', '__setstate__', '__getformat__', '__setformat__',    '__repr__', '__dir__', '__subclasses__', '__format__',))def _get_method(name, func):    "Turns a callable object (like a mock) into a real function"    def method(self, *args, **kw):        return func(self, *args, **kw)    method.__name__ = name    return method_magics = set(    '__%s__' % method for method in    ' '.join([magic_methods, numerics, inplace, right, extra]).split())_all_magics = _magics | _non_defaults_unsupported_magics = set((    '__getattr__', '__setattr__',    '__init__', '__new__', '__prepare__'    '__instancecheck__', '__subclasscheck__',    '__del__'))_calculate_return_value = {    '__hash__': lambda self: object.__hash__(self),    '__str__': lambda self: object.__str__(self),    '__sizeof__': lambda self: object.__sizeof__(self),    '__unicode__': lambda self: unicode(object.__str__(self)),}_return_values = {    '__lt__': NotImplemented,    '__gt__': NotImplemented,    '__le__': NotImplemented,    '__ge__': NotImplemented,    '__int__': 1,    '__contains__': False,    '__len__': 0,    '__exit__': False,    '__complex__': 1j,    '__float__': 1.0,    '__bool__': True,    '__nonzero__': True,    '__oct__': '1',    '__hex__': '0x1',    '__long__': long(1),    '__index__': 1,}def _get_eq(self):    def __eq__(other):        ret_val = self.__eq__._mock_return_value        if ret_val is not DEFAULT:            return ret_val        return self is other    return __eq__def _get_ne(self):    def __ne__(other):        if self.__ne__._mock_return_value is not DEFAULT:            return DEFAULT        return self is not other    return __ne__def _get_iter(self):    def __iter__():        ret_val = self.__iter__._mock_return_value        if ret_val is DEFAULT:            return iter([])        # if ret_val was already an iterator, then calling iter on it should        # return the iterator unchanged        return iter(ret_val)    return __iter___side_effect_methods = {    '__eq__': _get_eq,    '__ne__': _get_ne,    '__iter__': _get_iter,}def _set_return_value(mock, method, name):    fixed = _return_values.get(name, DEFAULT)    if fixed is not DEFAULT:        method.return_value = fixed        return    return_calulator = _calculate_return_value.get(name)    if return_calulator is not None:        try:            return_value = return_calulator(mock)        except AttributeError:            # XXXX why do we return AttributeError here?            #      set it as a side_effect instead?            return_value = AttributeError(name)        method.return_value = return_value        return    side_effector = _side_effect_methods.get(name)    if side_effector is not None:        method.side_effect = side_effector(mock)class MagicMixin(object):    def __init__(self, *args, **kw):        # 添加所有未存在的魔术方法        self._mock_set_magics()  # make magic work for kwargs in init        # 调用其他父类的__init__方法，添加_mock_methods方法        _safe_super(MagicMixin, self).__init__(*args, **kw)        # 修复被其他父类__init__方法破坏的mock方法        self._mock_set_magics()  # fix magic broken by upper level init    def _mock_set_magics(self):        these_magics = _magics        # 第一次执行的时候_mock_methods是None        if getattr(self, "_mock_methods", None) is not None:            these_magics = _magics.intersection(self._mock_methods)            #these_magics=mock的魔术方法            remove_magics = set()            remove_magics = _magics - these_magics            for entry in remove_magics:                if entry in type(self).__dict__:                    # remove unneeded magic methods                    # 删除没mock的其他魔术方法                    delattr(self, entry)        # don't overwrite existing attributes if called a second time        # 添加mock魔术方法时不覆盖已存在的方法        these_magics = these_magics - set(type(self).__dict__)        _type = type(self)        for entry in these_magics:            # 添加、修复所有魔术方法            setattr(_type, entry, MagicProxy(entry, self))class NonCallableMagicMock(MagicMixin, NonCallableMock):    """A version of `MagicMock` that isn't callable."""    def mock_add_spec(self, spec, spec_set=False):        """Add a spec to a mock. `spec` can either be an object or a        list of strings. Only attributes on the `spec` can be fetched as        attributes from the mock.        If `spec_set` is True then only attributes on the spec can be set."""        self._mock_add_spec(spec, spec_set)        self._mock_set_magics()class MagicMock(MagicMixin, Mock):    u"""带魔术方法的mock类.    MagicMock is a subclass of Mock with default implementations    of most of the magic methods. You can use MagicMock without having to    configure the magic methods yourself.    If you use the `spec` or `spec_set` arguments then *only* magic    methods that exist in the spec will be created.    Attributes and the return value of a `MagicMock` will also be `MagicMocks`.    """    def mock_add_spec(self, spec, spec_set=False):        """Add a spec to a mock. `spec` can either be an object or a        list of strings. Only attributes on the `spec` can be fetched as        attributes from the mock.        If `spec_set` is True then only attributes on the spec can be set."""        self._mock_add_spec(spec, spec_set)        self._mock_set_magics()class MagicProxy(object):    u"""魔术代理类."""    def __init__(self, name, parent):        self.name = name        self.parent = parent    def __call__(self, *args, **kwargs):        # 魔术方法调用        m = self.create_mock()        return m(*args, **kwargs)    def create_mock(self):        entry = self.name        parent = self.parent        # 创建了一个Mock对象        m = parent._get_child_mock(name=entry, _new_name=entry,                                   _new_parent=parent)        setattr(parent, entry, m)        # 设置魔术方法返回值        _set_return_value(parent, m, entry)        return m    def __get__(self, obj, _type=None):        return self.create_mock()class _ANY(object):    """跟任何值比较都相等"""    "A helper object that compares equal to everything."    def __eq__(self, other):        return True    def __ne__(self, other):        return False    def __repr__(self):        return '<ANY>'ANY = _ANY()def _format_call_signature(name, args, kwargs):    message = '%s(%%s)' % name    formatted_args = ''    args_string = ', '.join([repr(arg) for arg in args])    def encode_item(item):        if six.PY2 and isinstance(item, unicode):            return item.encode("utf-8")        else:            return item    kwargs_string = ', '.join([        '%s=%r' % (encode_item(key), value) for key, value in sorted(kwargs.items())    ])    if args_string:        formatted_args = args_string    if kwargs_string:        if formatted_args:            formatted_args += ', '        formatted_args += kwargs_string    return message % formatted_argsclass _Call(tuple):    """    A tuple for holding the results of a call to a mock, either in the form    `(args, kwargs)` or `(name, args, kwargs)`.    If args or kwargs are empty then a call tuple will compare equal to    a tuple without those values. This makes comparisons less verbose::        _Call(('name', (), {})) == ('name',)        _Call(('name', (1,), {})) == ('name', (1,))        _Call(((), {'a': 'b'})) == ({'a': 'b'},)    The `_Call` object provides a useful shortcut for comparing with call::        _Call(((1, 2), {'a': 3})) == call(1, 2, a=3)        _Call(('foo', (1, 2), {'a': 3})) == call.foo(1, 2, a=3)    If the _Call has no name then it will match any name.    """    def __new__(cls, value=(), name=None, parent=None, two=False,                from_kall=True):        name = ''        args = ()        kwargs = {}        _len = len(value)        if _len == 3:            name, args, kwargs = value        elif _len == 2:            first, second = value            if isinstance(first, basestring):                name = first                if isinstance(second, tuple):                    args = second                else:                    kwargs = second            else:                args, kwargs = first, second        elif _len == 1:            value, = value            if isinstance(value, basestring):                name = value            elif isinstance(value, tuple):                args = value            else:                kwargs = value        if two:            return tuple.__new__(cls, (args, kwargs))        return tuple.__new__(cls, (name, args, kwargs))    def __init__(self, value=(), name=None, parent=None, two=False,                 from_kall=True):        self.name = name        self.parent = parent        self.from_kall = from_kall    def __eq__(self, other):        if other is ANY:            return True        try:            len_other = len(other)        except TypeError:            return False        self_name = ''        if len(self) == 2:            self_args, self_kwargs = self        else:            self_name, self_args, self_kwargs = self        other_name = ''        if len_other == 0:            other_args, other_kwargs = (), {}        elif len_other == 3:            other_name, other_args, other_kwargs = other        elif len_other == 1:            value, = other            if isinstance(value, tuple):                other_args = value                other_kwargs = {}            elif isinstance(value, basestring):                other_name = value                other_args, other_kwargs = (), {}            else:                other_args = ()                other_kwargs = value        elif len_other == 2:            # could be (name, args) or (name, kwargs) or (args, kwargs)            first, second = other            if isinstance(first, basestring):                other_name = first                if isinstance(second, tuple):                    other_args, other_kwargs = second, {}                else:                    other_args, other_kwargs = (), second            else:                other_args, other_kwargs = first, second        else:            return False        if self_name and other_name != self_name:            return False        # this order is important for ANY to work!        return (other_args, other_kwargs) == (self_args, self_kwargs)    def __ne__(self, other):        return not self.__eq__(other)    def __call__(self, *args, **kwargs):        if self.name is None:            return _Call(('', args, kwargs), name='()')        name = self.name + '()'        return _Call((self.name, args, kwargs), name=name, parent=self)    def __getattr__(self, attr):        if self.name is None:            return _Call(name=attr, from_kall=False)        name = '%s.%s' % (self.name, attr)        return _Call(name=name, parent=self, from_kall=False)    def count(self, *args, **kwargs):        return self.__getattr__('count')(*args, **kwargs)    def index(self, *args, **kwargs):        return self.__getattr__('index')(*args, **kwargs)    def __repr__(self):        if not self.from_kall:            name = self.name or 'call'            if name.startswith('()'):                name = 'call%s' % name            return name        if len(self) == 2:            name = 'call'            args, kwargs = self        else:            name, args, kwargs = self            if not name:                name = 'call'            elif not name.startswith('()'):                name = 'call.%s' % name            else:                name = 'call%s' % name        return _format_call_signature(name, args, kwargs)    def call_list(self):        """For a call object that represents multiple calls, `call_list`        returns a list of all the intermediate calls as well as the        final call."""        vals = []        thing = self        while thing is not None:            if thing.from_kall:                vals.append(thing)            thing = thing.parent        return _CallList(reversed(vals))call = _Call(from_kall=False)def create_autospec(spec, spec_set=False, instance=False, _parent=None,                    _name=None, **kwargs):    u"""创建autospec mock对象."""    """Create a mock object using another object as a spec. Attributes on the    mock will use the corresponding attribute on the `spec` object as their    spec.    将其他对象作为spec参数，mock对象将包含spec对象中的属性    Functions or methods being mocked will have their arguments checked    to check that they are called with the correct signature.    被mock的方法将会检查方法签名    If `spec_set` is True then attempting to set attributes that don't exist    on the spec object will raise an `AttributeError`.    如果spec_set=True，则设置不存在的属性时将会报AttributeError异常    If a class is used as a spec then the return value of the mock (the    instance of the class) will have the same spec. You can use a class as the    spec for an instance object by passing `instance=True`. The returned mock    will only be callable if instances of the mock are callable.    `create_autospec` also takes arbitrary keyword arguments that are passed to    the constructor of the created mock."""    if _is_list(spec):        # can't pass a list instance to the mock constructor as it will be        # interpreted as a list of strings        spec = type(spec)    is_type = isinstance(spec, ClassTypes)    _kwargs = {'spec': spec}    if spec_set:        _kwargs = {'spec_set': spec}    elif spec is None:        # None we mock with a normal mock without a spec        _kwargs = {}    if _kwargs and instance:        _kwargs['_spec_as_instance'] = True    _kwargs.update(kwargs)    # 默认是MagicMock对象    Klass = MagicMock    if type(spec) in DescriptorTypes:        # descriptors don't have a spec        # because we don't know what type they return        _kwargs = {}    elif not _callable(spec):        # 根据spec选择mock类型        Klass = NonCallableMagicMock    elif is_type and instance and not _instance_callable(spec):        Klass = NonCallableMagicMock    _name = _kwargs.pop('name', _name)    _new_name = _name    if _parent is None:        # for a top level object no _new_name should be set        _new_name = ''    # 创建mock对象    mock = Klass(parent=_parent, _new_parent=_parent, _new_name=_new_name,                 name=_name, **_kwargs)    if isinstance(spec, FunctionTypes):        # should only happen at the top level because we don't        # recurse for functions        # 添加签名检查        mock = _set_signature(mock, spec)    else:        # 设置参数检验方法        _check_signature(spec, mock, is_type, instance)    if _parent is not None and not instance:        _parent._mock_children[_name] = mock    if is_type and not instance and 'return_value' not in kwargs:        mock.return_value = create_autospec(spec, spec_set, instance=True,                                            _name='()', _parent=mock)    for entry in dir(spec):        # 设置对象属性        if _is_magic(entry):            # MagicMock already does the useful magic methods for us            continue        # XXXX do we need a better way of getting attributes without        # triggering code execution (?) Probably not - we need the actual        # object to mock it so we would rather trigger a property than mock        # the property descriptor. Likewise we want to mock out dynamically        # provided attributes.        # XXXX what about attributes that raise exceptions other than        # AttributeError on being fetched?        # we could be resilient against it, or catch and propagate the        # exception when the attribute is fetched from the mock        try:            original = getattr(spec, entry)        except AttributeError:            continue        kwargs = {'spec': original}        if spec_set:            kwargs = {'spec_set': original}        if not isinstance(original, FunctionTypes):            new = _SpecState(original, spec_set, mock, entry, instance)            mock._mock_children[entry] = new        else:            parent = mock            if isinstance(spec, FunctionTypes):                parent = mock.mock            skipfirst = _must_skip(spec, entry, is_type)            kwargs['_eat_self'] = skipfirst            new = MagicMock(parent=parent, name=entry, _new_name=entry,                            _new_parent=parent,                            **kwargs)            mock._mock_children[entry] = new            # 设置方法签名检查            _check_signature(original, new, skipfirst=skipfirst)        # so functions created with _set_signature become instance attributes,        # *plus* their underlying mock exists in _mock_children of the parent        # mock. Adding to _mock_children may be unnecessary where we are also        # setting as an instance attribute?        if isinstance(new, FunctionTypes):            setattr(mock, entry, new)    return mockdef _must_skip(spec, entry, is_type):    """    Return whether we should skip the first argument on spec's `entry`    attribute.    """    if not isinstance(spec, ClassTypes):        if entry in getattr(spec, '__dict__', {}):            # instance attribute - shouldn't skip            return False        spec = spec.__class__    if not hasattr(spec, '__mro__'):        # old style class: can't have descriptors anyway        return is_type    for klass in spec.__mro__:        result = klass.__dict__.get(entry, DEFAULT)        if result is DEFAULT:            continue        if isinstance(result, (staticmethod, classmethod)):            return False        elif isinstance(getattr(result, '__get__', None), MethodWrapperTypes):            # Normal method => skip if looked up on type            # (if looked up on instance, self is already skipped)            return is_type        else:            return False    # shouldn't get here unless function is a dynamically provided attribute    # XXXX untested behaviour    return is_typedef _get_class(obj):    try:        return obj.__class__    except AttributeError:        # it is possible for objects to have no __class__        return type(obj)class _SpecState(object):    def __init__(self, spec, spec_set=False, parent=None,                 name=None, ids=None, instance=False):        self.spec = spec        self.ids = ids        self.spec_set = spec_set        self.parent = parent        self.instance = instance        self.name = nameFunctionTypes = (    # python function    type(create_autospec),    # instance method    type(ANY.__eq__),)MethodWrapperTypes = (    type(ANY.__eq__.__get__),)file_spec = Nonedef _iterate_read_data(read_data):    """迭代读取器"""    # Helper for mock_open:    # Retrieve lines from read_data via a generator so that separate calls to    # readline, read, and readlines are properly interleaved    sep = b'\n' if isinstance(read_data, bytes) else '\n'    data_as_list = [l + sep for l in read_data.split(sep)]    if data_as_list[-1] == sep:        # If the last line ended in a newline, the list comprehension will have an        # extra entry that's just a newline.  Remove this.        data_as_list = data_as_list[:-1]    else:        # If there wasn't an extra newline by itself, then the file being        # emulated doesn't have a newline to end the last line  remove the        # newline that our naive format() added        data_as_list[-1] = data_as_list[-1][:-1]    for line in data_as_list:        yield linedef mock_open(mock=None, read_data=''):    """打开文件补丁"""    """    A helper function to create a mock to replace the use of `open`. It works    for `open` called directly or used as a context manager.    The `mock` argument is the mock object to configure. If `None` (the    default) then a `MagicMock` will be created for you, with the API limited    to methods or attributes available on standard file handles.    `read_data` is a string for the `read` methoddline`, and `readlines` of the    file handle to return.  This is an empty string by default.    """    def _readlines_side_effect(*args, **kwargs):        if handle.readlines.return_value is not None:            return handle.readlines.return_value        return list(_state[0])    def _read_side_effect(*args, **kwargs):        if handle.read.return_value is not None:            return handle.read.return_value        return type(read_data)().join(_state[0])    def _readline_side_effect():        if handle.readline.return_value is not None:            while True:                yield handle.readline.return_value        for line in _state[0]:            yield line    global file_spec    if file_spec is None:        # set on first use        if six.PY3:            import _io            file_spec = list(set(dir(_io.TextIOWrapper)).union(set(dir(_io.BytesIO))))        else:            file_spec = file    if mock is None:        mock = MagicMock(name='open', spec=open)    handle = MagicMock(spec=file_spec)    handle.__enter__.return_value = handle    _state = [_iterate_read_data(read_data), None]    handle.write.return_value = None    handle.read.return_value = None    handle.readline.return_value = None    handle.readlines.return_value = None    handle.read.side_effect = _read_side_effect    _state[1] = _readline_side_effect()    handle.readline.side_effect = _state[1]    handle.readlines.side_effect = _readlines_side_effect    def reset_data(*args, **kwargs):        _state[0] = _iterate_read_data(read_data)        if handle.readline.side_effect == _state[1]:            # 在没有更改的情况下才设置            # Only reset the side effect if the user hasn't overridden it.            _state[1] = _readline_side_effect()            handle.readline.side_effect = _state[1]        return DEFAULT    mock.side_effect = reset_data    mock.return_value = handle    return mockclass PropertyMock(Mock):    u"""给属性打补丁"""    """    A mock intended to be used as a property, or other descriptor, on a class.    `PropertyMock` provides `__get__` and `__set__` methods so you can specify    a return value when it is fetched.    Fetching a `PropertyMock` instance from an object calls the mock, with    no args. Setting it calls the mock with the value being set.    """    def _get_child_mock(self, **kwargs):        return MagicMock(**kwargs)    def __get__(self, obj, obj_type):        return self()    def __set__(self, obj, val):        self(val)

总结：mock源码中用到了python中一些比较高级的语法糖，比如lambda生成一个匿名函数，有yield的函数已不是一个函数，而是一个生产器，用于生成可迭代对象，有next方法，可用于循环迭代中，type的一个实例就是一个类，还有就是涉及一些魔术方法，比如调用__call__，上下文管理__enter__、__exit__，创建对象__new__，初始化对象__init__，取得、设置属性__getattr__、__setattr__，还有大量使用了python装饰器。mock的实现原理主要是调用实际方法前调用__enter__给指定对象打补丁，并保存原始对象，方法调用后调用__exit__进行原始对象恢复，其中并覆写Mock对象的__call__使可以统计调用情况，覆写__getattr__可访问任意属性，autospec情况下获取函数签名进行参数检查。mock常用的就是mock.patch装饰器，可以作用在整个测试类上，也可以作用在单个测试方法上，当作用在测试类上时，会给测试类所有已test开头的测试方法都打上补丁。除了mock.patch，还提供一些其他实用工具，比如mock.patch.object给指定对象中的属性打补丁，patch.dict给dict的值打补丁，patch.multiple同时给一个对象的多个属性打补丁，patch.stopall取消所有补丁，mock_open模拟文件打开读取操作。