def test_form_response(self):
        block = SnippetChooserBlock(AdvertWithCustomPrimaryKey)
        test_advert = AdvertWithCustomPrimaryKey.objects.get(pk='advert/01')

        value = block.value_from_datadict({'advertwithcustomprimarykey': str(test_advert.pk)}, {}, 'advertwithcustomprimarykey')
        self.assertEqual(value, test_advert)

        empty_value = block.value_from_datadict({'advertwithcustomprimarykey': ''}, {}, 'advertwithcustomprimarykey')
        self.assertEqual(empty_value, None)

    def test_deserialize(self):
        """The serialized value of a SnippetChooserBlock (an ID) should deserialize to a snippet instance"""
        block = SnippetChooserBlock(AdvertWithCustomPrimaryKey)
        test_advert = AdvertWithCustomPrimaryKey.objects.get(pk='advert/01')

        self.assertEqual(block.to_python(test_advert.pk), test_advert)

        # None should deserialize to None
        self.assertEqual(block.to_python(None), None)

    def test_serialize(self):
        """The value of a SnippetChooserBlock (a snippet instance) should serialize to an ID"""
        block = SnippetChooserBlock(AdvertWithCustomPrimaryKey)
        test_advert = AdvertWithCustomPrimaryKey.objects.get(pk='advert/01')

        self.assertEqual(block.get_prep_value(test_advert), test_advert.pk)

        # None should serialize to None
        self.assertEqual(block.get_prep_value(None), None)

    def test_form_render(self):
        block = SnippetChooserBlock(AdvertWithCustomPrimaryKey, help_text="pick an advert, any advert")

        empty_form_html = block.render_form(None, 'advertwithcustomprimarykey')
        self.assertInHTML('<input id="advertwithcustomprimarykey" name="advertwithcustomprimarykey" placeholder="" type="hidden" />', empty_form_html)
        self.assertIn('createSnippetChooser("advertwithcustomprimarykey", "tests/advertwithcustomprimarykey");', empty_form_html)

        test_advert = AdvertWithCustomPrimaryKey.objects.get(pk='advert/01')
        test_advert_form_html = block.render_form(test_advert, 'advertwithcustomprimarykey')
        expected_html = '<input id="advertwithcustomprimarykey" name="advertwithcustomprimarykey" placeholder="" type="hidden" value="%s" />' % test_advert.pk
        self.assertInHTML(expected_html, test_advert_form_html)
        self.assertIn("pick an advert, any advert", test_advert_form_html)

    def test_clean(self):
        required_block = SnippetChooserBlock(AdvertWithCustomPrimaryKey)
        nonrequired_block = SnippetChooserBlock(AdvertWithCustomPrimaryKey, required=False)
        test_advert = AdvertWithCustomPrimaryKey.objects.get(pk='advert/01')

        self.assertEqual(required_block.clean(test_advert), test_advert)
        with self.assertRaises(ValidationError):
            required_block.clean(None)

        self.assertEqual(nonrequired_block.clean(test_advert), test_advert)
        self.assertEqual(nonrequired_block.clean(None), None)

 def test_reference_model_by_string(self):
     block = SnippetChooserBlock('tests.Advert')
     test_advert = Advert.objects.get(text='test_advert')
     self.assertEqual(block.to_python(test_advert.id), test_advert)