断言在特定实例上调用了 PropertyMock答案

【问题标题】：Assert that a PropertyMock was called on a specific instance断言在特定实例上调用了 PropertyMock
【发布时间】：2016-05-31 18:55:23
【问题描述】：

我已经成功地用PropertyMock 模拟了一个属性，但我不知道如何检查该类的哪个实例调用了该属性。如何断言该属性是在一个对象上调用的，而不是在另一个对象上调用的？

这是一个示例，我想断言 foo1.is_big 被调用，而 foo2.is_big 未被调用：

from mock import PropertyMock, patch


class Foo(object):
    def __init__(self, size):
        self.size = size

    @property
    def is_big(self):
        return self.size > 5

f = Foo(3)
g = Foo(10)
assert not f.is_big
assert g.is_big

with patch('__main__.Foo.is_big', new_callable=PropertyMock) as mock_is_big:
    mock_is_big.return_value = True
    foo1 = Foo(4)
    foo2 = Foo(9)

    should_pass = False
    if should_pass:
        is_big = foo1.is_big
    else:
        is_big = foo2.is_big
    assert is_big
    # How can I make this pass when should_pass is True, and fail otherwise?
    mock_is_big.assert_called_once_with()

print('Done.')

当其中任何一个被调用时，当前代码都会通过。

【问题讨论】：

标签： python unit-testing mocking

【解决方案1】：

也许有更好的方法，但我通过创建 PropertyMock 的子类来实现它，该子类将调用它的实例记录为模拟调用的参数之一。

from mock import PropertyMock, patch


class Foo(object):
    def __init__(self, size):
        self.size = size

    @property
    def is_big(self):
        return self.size > 5


class PropertyInstanceMock(PropertyMock):
    """Like PropertyMock, but records the instance that was called."""

    def __get__(self, obj, obj_type):
        return self(obj)

    def __set__(self, obj, val):
        self(obj, val)


with patch("__main__.Foo.is_big", new_callable=PropertyInstanceMock) as mock_is_big:
    mock_is_big.return_value = True
    foo1 = Foo(4)
    foo2 = Foo(9)

    should_pass = False
    if should_pass:
        is_big = foo1.is_big
    else:
        is_big = foo2.is_big
    assert is_big
    # Now this passes when should_pass is True, and fails otherwise.
    mock_is_big.assert_called_once_with(foo1)

print("Done.")

【讨论】：