def METHOD_NAME(self):
    """Test the UI registry with content negotiation for json/yaml."""
    identifier = "0000001"
    for accept, loads in [
        ("application/json", json.loads),
        ("application/yaml", yaml.safe_load),
    ]:
        with self.subTest(format=format), self.app.test_client() as client:
            res = client.get(f"/collection/{identifier}", headers={"Accept": accept})
            self.assertEqual(
                200,
                res.status_code,
                msg=f"Failed on {identifier} to accept {accept} ({format})",
            )
            self.assertEqual({accept}, {t for t, _ in res.request.accept_mimetypes})
            collection = Collection(**loads(res.text))
            self.assertEqual(self.manager.collections[identifier], collection)