使用pytest，我如何在有和没有配置文件的情况下测试Flask应用的配置？

 def test_app_without_config():

     app = Flask(__name__)

     app.config.from_mapping(

         DEBUG=True,

         SECRET_KEY='mysecretkey',

         DATABASE='mydatabase'

     )

     assert app.config['DEBUG'] is True

     assert app.config['SECRET_KEY'] == 'mysecretkey'

     assert app.config['DATABASE'] == 'mydatabase'

 ```

 def test_app_with_config():

     app = Flask(__name__)

     app.config.from_pyfile('config.py')

     assert app.config['DEBUG'] is True

     assert app.config['SECRET_KEY'] == 'mysecretkey'

     assert app.config['DATABASE'] == 'mydatabase'

 ```