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如何使用python模拟直接模拟超类?

如何使用python模拟直接模拟超类?

我按照kindall的建议玩弄了super()。不幸的是,经过大量的努力,处理复杂的继承案例变得非常复杂。

经过一些工作,我意识到当通过MRO解析属性时,super()直接访问类的__dict__(它不会进行getattr类型的调用)。解决方案是扩展一个ockock.MagicMock()对象,并用一个类包装它以完成此操作。然后,可以将包装的类放在子类的__bases__变量中。

包装的对象将目标类的所有定义的属性反映到包装类的__dict__,以便super()调用解析为内部MagicMock()中正确修补的属性

以下代码是到目前为止我发现可以使用的解决方案。请注意,我实际上是在上下文处理程序中实现的。另外,如果从其他模块导入,则必须注意修补适当的名称空间。

这是说明此方法的简单示例:

from mock import MagicMock
import inspect


class _WrappedMagicMock(MagicMock):
    def __init__(self, *args, **kwds):
        object.__setattr__(self, '_mockclass_wrapper', None)
        super(_WrappedMagicMock, self).__init__(*args, **kwds)

    def wrap(self, cls):
        # get defined attribtues of spec class that need to be preset
        base_attrs = dir(type('Dummy', (object,), {}))
        attrs = inspect.getmembers(self._spec_class)
        new_attrs = [a[0] for a in attrs if a[0] not in base_attrs]

        # pre set mocks for attributes in the target mock class
        for name in new_attrs:
            setattr(cls, name, getattr(self, name))

        # eat up any attempts to initialize the target mock class
        setattr(cls, '__init__', lambda *args, **kwds: None)

        object.__setattr__(self, '_mockclass_wrapper', cls)

    def unwrap(self):
        object.__setattr__(self, '_mockclass_wrapper', None)

    def __setattr__(self, name, value):
        super(_WrappedMagicMock, self).__setattr__(name, value)

        # be sure to reflect to changes wrapper class if activated
        if self._mockclass_wrapper is not None:
            setattr(self._mockclass_wrapper, name, value)

    def _get_child_mock(self, **kwds):
        # when created children mocks need only be MagicMocks
        return MagicMock(**kwds)


class A(object):
    x = 1

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

    def get_value_direct(self):
        return self.value

    def get_value_indirect(self):
        return self.value


class B(A):
    def __init__(self, value):
        super(B, self).__init__(value)

    def f(self):
        return 2

    def get_value_direct(self):
        return A.get_value_direct(self)

    def get_value_indirect(self):
        return super(B, self).get_value_indirect()

# nominal behavior
b = B(3)
assert b.get_value_direct() == 3
assert b.get_value_indirect() == 3
assert b.f() == 2
assert b.x == 1

# using mock class
MockClass = type('MockClassWrapper', (), {})
mock = _WrappedMagicMock(A)
mock.wrap(MockClass)

# patch the mock in
B.__bases__ = (MockClass, )
A = MockClass

# set values within the mock
mock.x = 0
mock.get_value_direct.return_value = 0
mock.get_value_indirect.return_value = 0

# mocked behavior
b = B(7)
assert b.get_value_direct() == 0
assert b.get_value_indirect() == 0
assert b.f() == 2
assert b.x == 0
python 2022/1/1 18:41:20 有279人围观

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