def METHOD_NAME(self, mock_client, base_path):
    self.backend.base_path = base_path
    self.backend.delete(b"mykey")
    mock_client.get_blob_client.assert_called_once_with(
        container="celery", blob=base_path + "mykey")
    mock_client.get_blob_client.return_value \
        .delete_blob.assert_called_once()