How to test custom Django forms clean/save methods?

Question

Most of the time I have to change/extend the default form save/clean methods. However I'm not really sure how to test the custom save/clean methods.

Most of the time my tests are like:

response = self.client.post(reverse('example:view_name'), kwargs={'example, self.example'})
self.assertEqual(200, response.status_code)
self.assertTemplateUsed('example.html', response)

Using self.client.post from Django's TestCase class, to capture the response isn't enough and definitely doesn't cover/test custom save and clean.

What's your practice of testing forms? In my opinion what I did above is wrong, since it's more of an integration test that goes through the view to get to the form.

Answer 1

Create the form directly in the tests, and call is_valid method (clean is called by is_valid); check whether it validate correctly. Same for the save method.

For example:

from django.contrib.auth.forms import (UserCreationForm, ...)

...

class UserCreationFormTest(TestCase):

    def test_user_already_exists(self):
        data = {
            'username': 'testclient',
            'password1': 'test123',
            'password2': 'test123',
        }
        form = UserCreationForm(data)
        self.assertFalse(form.is_valid())
        self.assertEqual(
            form["username"].errors,
            [force_text(User._meta.get_field('username').error_messages['unique'])])

(Above code came from the django source code - django/contrib/auth/tests/test_forms.py).

---

BTW, the parameters for assertTemplateUsed are response, template_name, ..., not template_name, response, .....

The last line in the code in the question should be:

self.assertTemplateUsed(response, 'example.html')