django/tests/modeltests/model_forms/tests.py

from django.test import TestCase
from django import forms
from models import Category


class IncompleteCategoryFormWithFields(forms.ModelForm):
    """
    A form that replaces the model's url field with a custom one. This should
    prevent the model field's validation from being called.
    """
    url = forms.CharField(required=False)

    class Meta:
        fields = ('name', 'slug')
        model = Category

class IncompleteCategoryFormWithExclude(forms.ModelForm):
    """
    A form that replaces the model's url field with a custom one. This should
    prevent the model field's validation from being called.
    """
    url = forms.CharField(required=False)

    class Meta:
        exclude = ['url']
        model = Category


class ValidationTest(TestCase):
    def test_validates_with_replaced_field_not_specified(self):
        form = IncompleteCategoryFormWithFields(data={'name': 'some name', 'slug': 'some-slug'})
        assert form.is_valid()

    def test_validates_with_replaced_field_excluded(self):
        form = IncompleteCategoryFormWithExclude(data={'name': 'some name', 'slug': 'some-slug'})
        assert form.is_valid()