python - 具有 ModelChoiceField 和模拟数据的 UnitTest ModelForm

Question

我一直在尝试为我的 ModelForm 编写单元测试，它有一个 ModelChoiceField。我正在使用模拟数据创建 Form 实例。

这是我的模型:

# models.py
class Menu(models.Model):
    dish = models.ForeignKey(Dish, default=None)
    price = models.DecimalField(max_digits=7, decimal_places=2)

# forms.py
class MenuForm(forms.ModelForm):
    class Meta:
        model = Menu
        fields = ('dish', 'price',)

    def clean(self):
        cleaned_data = super(MenuForm, self).clean()
        price = cleaned_data.get('price', None)
        dish = cleaned_data.get('dish', None)

        # Some validation below
        if price < 70:
            self.add_error('price', 'Min price threshold')
            return cleaned_data

这是我的测试用例:

class MenuFormTest(TestCase):
    def test_price_threshold(self):
        mock_dish = mock.Mock(spec=Dish)
        form_data = {
            'dish': mock_dish,
            'price': 80,
        }
        form = forms.MenuForm(data=form_data)
        self.assertTrue(form.is_valid())

失败并出现以下错误:

<ul class="errorlist"><li>dish<ul class="errorlist"><li>Select a valid choice. That choice is not one of the available choices.</li></ul></li></ul>

如何避免抛出该错误。 form.is_valid() 在那里应该是 True。有什么方法可以修补 ModelChoiceField 的 queryset？我尝试修补表单的 dish 字段 clean() 方法，如下所示:

form = forms.MenuForm(data=form_data)
dish_clean_patcher = mock.patch.object(form.fields['dish'], 'clean')
dish_clean_patch = dish_clean_patcher.start()
dish_clean_patch.return_value = mock_dish

self.assertTrue(form.is_valid())

然后看起来，在 _post_clean() 方法中将表单数据保存到模型实例时失败了。这是回溯:

Traceback (most recent call last):
  File "/home/vagrant/venv/local/lib/python2.7/site-packages/mock/mock.py", line 1305, in patched
    return func(*args, **keywargs)
  File "/vagrant/myapp/tests/test_forms.py", line 51, in test_price_threshold
    self.assertFalse(form.is_valid())
  File "/home/vagrant/venv/local/lib/python2.7/site-packages/django/forms/forms.py", line 185, in is_valid
    return self.is_bound and not self.errors
  File "/home/vagrant/venv/local/lib/python2.7/site-packages/django/forms/forms.py", line 177, in errors
    self.full_clean()
  File "/home/vagrant/venv/local/lib/python2.7/site-packages/django/forms/forms.py", line 396, in full_clean
    self._post_clean()
  File "/home/vagrant/venv/local/lib/python2.7/site-packages/django/forms/models.py", line 427, in _post_clean
    self.instance = construct_instance(self, self.instance, opts.fields, construct_instance_exclude)
  File "/home/vagrant/venv/local/lib/python2.7/site-packages/django/forms/models.py", line 62, in construct_instance
    f.save_form_data(instance, cleaned_data[f.name])
  File "/home/vagrant/venv/local/lib/python2.7/site-packages/django/db/models/fields/__init__.py", line 874, in save_form_data
    setattr(instance, self.name, data)
  File "/home/vagrant/venv/local/lib/python2.7/site-packages/django/db/models/fields/related.py", line 632, in __set__
    instance._state.db = router.db_for_write(instance.__class__, instance=value)
  File "/home/vagrant/venv/local/lib/python2.7/site-packages/django/db/utils.py", line 300, in _route_db
    if instance is not None and instance._state.db:
  File "/home/vagrant/venv/local/lib/python2.7/site-packages/mock/mock.py", line 716, in __getattr__
    raise AttributeError("Mock object has no attribute %r" % name)
AttributeError: Mock object has no attribute '_state'

我如何避免那部分？我根本不希望它查看 instance._state.db。

我是否正确地测试了表单？或者我应该通过修补 super(MenuForm, self).clean( ) 方法，并检查 form.errors?

Answer 1

我会说调用 form.is_valid() 是测试表单的好方法。不过，我不确定是否要模拟模型。

Internally the form is calling get_limit_choices_to on your dish field (Django 当前正在为您创建)。

You would need to mock the dish field's .queryset or get_limit_choices_to here ，(或调用堆栈中使此处的值变得毫无意义的其他地方)以某种方式实现您想要的。

或者，在您的测试中创建一个 Dish 并让 Django 的内部继续做他们正在做的事情会简单得多。

class MenuFormTest(TestCase):
    def test_price_threshold(self):
        dish = Dish.objects.create(
            # my values here
        )
        form_data = {
            'dish': dish.id,
            'price': 80,
        }
        form = MenuForm(data=form_data)
        self.assertTrue(form.is_valid())

如果您真的不想使用 Django 的测试数据库，一种策略可能是模拟 MenuForm.clean 和 MenuForm._post_clean:

class MenuFormTest(TestCase):
    def test_price_threshold(self):
        mock_dish = mock.Mock(spec=Dish)
        form_data = {
            'dish': 1,
            'price': 80,
        }
        form = MenuForm(data=form_data)
        form.fields['dish'].clean = lambda _: mock_dish
        form._post_clean = lambda : None
        self.assertTrue(form.is_valid())

如果您要进行此测试，您需要问问自己您的目标是什么。