code: def test_auth_header(self):
      # fake credentials
      os.environ.setdefault(
          "LIGHTNING_USER_ID", "7c8455e3-7c5f-4697-8a6d-105971d6b9bd"
      )
      os.environ.setdefault(
          "LIGHTNING_API_KEY", "e63fae57-2b50-498b-bc46-d6204cbf330e"
      )
      auth = login.Auth()
      auth.clear()
      auth.authenticate()
  
      assert "Basic" in auth.auth_header
      assert (
          auth.auth_header
          == "Basic N2M4NDU1ZTMtN2M1Zi00Njk3LThhNmQtMTA1OTcxZDZiOWJkOmU2M2ZhZTU3LTJiNTAtNDk4Yi1iYzQ2LWQ2MjA0Y2JmMzMwZQ=="  # noqa E501
      )
  
file_path: pytorch-lightning/tests/tests_app/utilities/test_login.py
imports: import os
  from unittest import mock
  import pytest
  import requests
  from lightning.app.utilities import login
label_desc: Use image node_id 5 for calling the TestAuthentication obj's underlying member method code with example usage: obj.test_auth_header() without return types