def test_serialize(self):
        block = EmbedBlock(required=False)

        block_val = EmbedValue('http://www.example.com/foo')
        serialized_val = block.get_prep_value(block_val)
        self.assertEqual(serialized_val, 'http://www.example.com/foo')

        serialized_empty_val = block.get_prep_value(None)
        self.assertEqual(serialized_empty_val, '')

    def test_render_form(self):
        """
        The form field for an EmbedBlock should be a text input containing
        the URL
        """
        block = EmbedBlock()

        form_html = block.render_form(EmbedValue('http://www.example.com/foo'), prefix='myembed')
        self.assertIn('<input ', form_html)
        self.assertIn('value="http://www.example.com/foo"', form_html)

    def test_render(self, get_embed):
        get_embed.return_value = Embed(html='<h1>Hello world!</h1>')

        block = EmbedBlock()
        html = block.render('http://www.example.com')

        # Check that get_embed was called correctly
        get_embed.assert_any_call('http://www.example.com')

        # Check that the embed was in the returned HTML
        self.assertIn('<h1>Hello world!</h1>', html)

    def test_value_from_form(self):
        """
        EmbedBlock should be able to turn a URL submitted as part of a form
        back into an EmbedValue
        """
        block = EmbedBlock(required=False)

        block_val = block.value_from_datadict({'myembed': 'http://www.example.com/foo'}, {}, prefix='myembed')
        self.assertIsInstance(block_val, EmbedValue)
        self.assertEqual(block_val.url, 'http://www.example.com/foo')

        # empty value should result in None
        empty_val = block.value_from_datadict({'myembed': ''}, {}, prefix='myembed')
        self.assertEqual(empty_val, None)

    def test_deserialize(self):
        """
        Deserialising the JSONish value of an EmbedBlock (a URL) should give us an EmbedValue
        for that URL
        """
        block = EmbedBlock(required=False)

        block_val = block.to_python('http://www.example.com/foo')
        self.assertIsInstance(block_val, EmbedValue)
        self.assertEqual(block_val.url, 'http://www.example.com/foo')

        # empty values should yield None
        empty_block_val = block.to_python('')
        self.assertEqual(empty_block_val, None)

    def test_render(self, get_embed):
        get_embed.return_value = Embed(html='<h1>Hello world!</h1>')

        block = EmbedBlock()
        block_val = block.to_python('http://www.example.com/foo')

        temp = template.Template('embed: {{ embed }}')
        context = template.Context({'embed': block_val})
        result = temp.render(context)

        # Check that the embed was in the returned HTML
        self.assertIn('<h1>Hello world!</h1>', result)

        # Check that get_embed was called correctly
        get_embed.assert_any_call('http://www.example.com/foo')

    def test_clean(self):
        required_block = EmbedBlock()
        nonrequired_block = EmbedBlock(required=False)

        # a valid EmbedValue should return the same value on clean
        cleaned_value = required_block.clean(EmbedValue('http://www.example.com/foo'))
        self.assertIsInstance(cleaned_value, EmbedValue)
        self.assertEqual(cleaned_value.url, 'http://www.example.com/foo')

        cleaned_value = nonrequired_block.clean(EmbedValue('http://www.example.com/foo'))
        self.assertIsInstance(cleaned_value, EmbedValue)
        self.assertEqual(cleaned_value.url, 'http://www.example.com/foo')

        # None should only be accepted for nonrequired blocks
        cleaned_value = nonrequired_block.clean(None)
        self.assertEqual(cleaned_value, None)

        with self.assertRaises(ValidationError):
            required_block.clean(None)

    def test_default(self):
        block1 = EmbedBlock()
        self.assertEqual(block1.get_default(), None)

        block2 = EmbedBlock(default='')
        self.assertEqual(block2.get_default(), None)

        block3 = EmbedBlock(default=None)
        self.assertEqual(block3.get_default(), None)

        block4 = EmbedBlock(default='http://www.example.com/foo')
        self.assertIsInstance(block4.get_default(), EmbedValue)
        self.assertEqual(block4.get_default().url, 'http://www.example.com/foo')

        block5 = EmbedBlock(default=EmbedValue('http://www.example.com/foo'))
        self.assertIsInstance(block5.get_default(), EmbedValue)
        self.assertEqual(block5.get_default().url, 'http://www.example.com/foo')