Python模拟类实例变量

Question

我正在使用 Python 的 mock 库。我知道如何按照document 模拟类实例方法：

>>> def some_function():
...     instance = module.Foo()
...     return instance.method()
...
>>> with patch('module.Foo') as mock:
...     instance = mock.return_value
...     instance.method.return_value = 'the result'
...     result = some_function()
...     assert result == 'the result'

但是，尝试模拟类实例变量但不起作用（以下示例中的instance.labels）：

>>> with patch('module.Foo') as mock:
...     instance = mock.return_value
...     instance.method.return_value = 'the result'
...     instance.labels = [1, 1, 2, 2]
...     result = some_function()
...     assert result == 'the result'

基本上我希望instance.labels在some_function下得到我想要的值。有什么提示吗？

Answer 1

此版本的some_function() 打印模拟labels 属性：

def some_function():
    instance = module.Foo()
    print instance.labels
    return instance.method()

我的module.py：

class Foo(object):

    labels = [5, 6, 7]

    def method(self):
        return 'some'

补丁和你的一样：

with patch('module.Foo') as mock:
    instance = mock.return_value
    instance.method.return_value = 'the result'
    instance.labels = [1,2,3,4,5]
    result = some_function()
    assert result == 'the result

完整的控制台会话：

>>> from mock import patch
>>> import module
>>> 
>>> def some_function():
...     instance = module.Foo()
...     print instance.labels
...     return instance.method()
... 
>>> some_function()
[5, 6, 7]
'some'
>>> 
>>> with patch('module.Foo') as mock:
...     instance = mock.return_value
...     instance.method.return_value = 'the result'
...     instance.labels = [1,2,3,4,5]
...     result = some_function()
...     assert result == 'the result'
...     
... 
[1, 2, 3, 4, 5]
>>>

对我来说，您的代码正在工作。