模拟上下文中的计时，以使用具有auto_now_add = True的字段DateTimeField创建模型

问题描述

我想模拟计时，以便在测试期间可以将设置为的时间，将设置为DateTimeField的字段，例如:

I'd like to mock timing so that be able to set certain time to a field of type DateTimeField with auto_now_add=True during my tests e.g:

class MyModel:
    ...
    created_at = models.DateTimeField(auto_now_add=True)
    ...


class TestMyModel(TestCase):
    ...
    def test_something(self):
        # mock current time so that `created_at` be something like 1800-02-09T020000
        my_obj = MyModel.objects.create(<whatever>)
        # and here my_obj.created_at == 1800-02-09T000000

我知道当前日期为 总是 用于这种类型的字段，这就是为什么我正在寻找一种替代方法，以某种方式模拟系统时序，但只是在上下文中.

我尝试了一些方法，例如，使用freeze_time创建上下文，但是没有用:

I've tried some approaches, for instance, creating a context with freeze_time but didn't work:

with freeze_now("1800-02-09"):
    MyModel.objects.create(<whatever>)
    # here the created_at doesn't fit 1800-02-09

我猜是Ofc，这是由于auto_now_add=True时在幕后创建对象的机制.

Ofc I guess, this is due to the machinery behind the scene to create the object when auto_now_add=True.

我不想删除auto_now_add=True和/或使用默认值.

I don't want to remove auto_now_add=True and/or use default values.

有没有一种方法可以模拟时间安排，以便我们可以使这种类型的字段在某些情况下获得我想要的时间?

Is there a way we can mock the timing so that we can make this type of field to get the time that I want in certain context?

我正在使用Django 1.9.6和Python 3.4

推荐答案

好的，我找到了一个解决方案，它基于模拟:

Okay, I have found a solution, it is based on mock:

def mock_now():
    return <mock time>

class TestMyModel(TestCase):
    ...
    @mock.patch('django.utils.timezone.now', mock_now)
    def test_as_decorator(self):
        ...
        my_obj = MyModel.objects.create(<whatever>)
        ...
         # here the created_at field has the mocking time :)

    def test_as_context_manager(self):
         mocked_dt = datetime.datetime(2015, 9, 3, 11, 15, 0)
         with mock.patch('django.utils.timezone.now', mock.Mock(return_value=mocked_dt)):
             my_obj = MyModel.objects.create(<whatever>)
             # here the created_at field has the mocking time :)

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