def METHOD_NAME(self):
    self.config.design_token_values = {
        "of": {"layout": {"background": {"value": "#ffffff"}}}
    }
    self.config.save()
    form_page = self.app.get(self.url)
    style_node = form_page.pyquery("head > style")
    self.assertTrue(style_node)
    self.assertEqual(
        style_node.text(), ":root { --of-layout-background: #ffffff; }"
    )