Check out apptim.com. It is specifically for testing client side performance for native mobile apps (Android and iOS) and it is also free to use.
Here is a good article that explains more about the tool and what there iss to know about it before getting started: https://blog.apptim.com/mobile-performance-testing/
So, there are three main components of mobile app performance:
When it comes to the backend, the things related to performance that are important to know when an app is under load are the server response times, database queries times, and the server’s resource usage.
This is where load testing with a tool like BlazeMeter ...
In Appium Latest Java client you can do it using
To disable Wifi and Data in Android:
To enabled WiFI and Data in Android:
To Enable and Disable Airplane mode in iOS ...