Django unit testing form with field assigned from request object

Question

I have this form

class PostCreationForm(forms.ModelForm):
    def form_valid(self, form):
        form.instance.author = self.request.user
        return super().form_valid(form)

and I'm trying to unit test it with this test

class PostCreationByFormTestCase(TestCase):
    def __init__(self, *args, **kwargs):
        super(PostCreationByFormTestCase, self).__init__(*args, **kwargs)
        self.CustomUser = get_user_model()

    def setUp(self):
        self.credentials = {
            'username': 'john_smith',
            'password': 'St0ngPassw0rd'
        }
        self.user = self.CustomUser.objects.create(
            username=self.credentials['username'],
            email='[email protected]',
            password=self.credentials['password'],
            first_name='John',
            last_name='Smith'
        )

    def test_simple_form(self):
        form_data = {
            'author': self.user,
            'title': 'Simple Post',
            'description': 'very good description',
        }
        form = PostCreationForm(form_data)
        self.assertTrue(form.is_valid)
        post = form.save()

the assert passes, but the form.save() produces django.db.utils.IntegrityError: null value in column "author_id" violates not-null constraint

I tried changing the form to

class PostCreationForm(forms.ModelForm):
    def form_valid(self, form):
        if not form.instance.author:
            form.instance.author = self.request.user
        return super().form_valid(form)

but it still does not work. I saw this as a recommended way to assign field to object if I don't want to take it as an input from the user as in this case where I want the author of the post to be the current user. How should I fix that in order to be able to test the form?

Answer 1

When checking whether a form is valid you need to call the method is_valid, it is not a property. Changing form.is_valid to form.is_valid() will work.

form_valid() however will not be called when you check for form.is_valid(), so you probably want to use the clean methods. An untested example:

class PostCreationForm(forms.ModelForm):

    def clean_author(self):
        author = self.cleaned_data.get('author')
        if not author:
            author = self.request.user
        return author