在unittest中模拟整个python类时无法引发异常

以下是原始类：

class Original(object):
    def __ init__(self, path):
        self.xml = None
        self.path = path
        self.convert() # <----- I can't modify anything in my class

    def convert(self):
        #some code here
        self.xml = external_api_call # <------------this generates objects for this property
        self.transform()

    def transform(self):
        #some code
        if not self._xml:
            raise Exception('None value')
        for project in self.xml.projects:
            try:
                value = getattr(project, "name")
            except AttributeError:
                raise Exception('AttributeError')
            print('Yes it worked')

它应该生成一个异常，但不会。我还尝试了不同的方法，例如模拟对象的副作用特性

mock_object._xml.return_value

---

不要修补

Original

，只修补外部api调用，比如使用mock.patch（“something.external\u api\u call”，lamda*args，**kws:None）：

mock_object._xml.return_value

@patch('something.Original')
def test_case_1(Original):
    Original.xml.side_effect = Exception()
    Original.transform()