How do I unit test (using pytest) the boxsdk Client?

Consider the following code that transfers a file from AWS S3 to Box using the boxsdk Client:

from boxsdk import JWTAuth, Clientimport boto3import jsonimport osimport tempfileclass BoxTransfer:    def __init__(self, bucket_name=None, file_name=None, folders=None) -> None:        self.bucket_name = bucket_name        self.file_name = file_name        self.folders = folders or {}        json_data = json.loads(os.environ['BOX_AUTHENTICATION'])        auth = JWTAuth(            client_id=json_data['boxAppSettings']['clientID'],            client_secret=json_data['boxAppSettings']['clientSecret'],            enterprise_id=json_data['enterpriseID'],            jwt_key_id=json_data['boxAppSettings']['appAuth']['publicKeyID'],            rsa_private_key_data=json_data['boxAppSettings']['appAuth']['privateKey'],            rsa_private_key_passphrase=json_data['boxAppSettings']['appAuth']['passphrase']        )        self.box_client = Client(auth)        self.folder = None    def get_user_id(self):        my_user = self.box_client.user().get()    def upload_file(self):        self.get_user_id()        with tempfile.NamedTemporaryFile() as tmp:            s3 = boto3.client('s3')            s3.download_fileobj(self.bucket_name, self.file_name, tmp)            tmp.seek(0)            s3_folder_name = self.file_name.split("/")[0]            s3_file_name = self.file_name.split("/")[-1]            s3_box_folder = self.folders[s3_folder_name]['box_folder']            self.folder = self.box_client.folder(s3_box_folder)            self.folder.upload(file_path=tmp.name, file_name=s3_file_name)

How would I write a unit test (in pytest) to test?

self.box_client = Client(auth)

The issue is the auth part. I've tried mocking the Oauth2 token:

@patch('os.environ', {'BOX_AUTHENTICATION': '{"boxAppSettings": {"clientID": "id", "clientSecret": "secret", "appAuth": {"publicKeyID": "key_id", "privateKey": "private_key", "passphrase": "passphrase"}}, "enterpriseID": "enterprise_id"}'})    @patch('boxsdk.Client')    def setUp(self, mock_box_client):        self.bucket_name = 'test_bucket'        self.file_name = 'test_file'        self.folders = {'test_folder': {'box_folder': 'box_folder_id'}}        self.box_transfer = BoxTransfer(self.bucket_name, self.file_name, self.folders)        self.mock_box_client = mock_box_client

But, it errors with the message:

('Could not deserialize key data. The data may be in an incorrectformat, it may be encrypted with an unsupported algorithm, or it maybe an unsupported key type (e.g. EC curves with explicitparameters).', [<OpenSSLError(code=503841036, lib=60, reason=524556,reason_text=unsupported)>])