android applications interactions

I have a problem and a don't know how to solve it. I saw some tools for automation testing for android apps, like appium and others. They connect to the android device, emulator, from outside the device and open the application to be tested. I want to know how can i build a native android app that can to the same thing. Open another application and start executing different operations on the UI of that app. For a simple example, let's say i have a social app that i want to test. I want another that runs on the phone that opens my social app and starts running some operations like searching inside the app, clicking on different posts, liking post, s.o. Is there a way to do this? Are there any frameworks or methods for doing this?

Regards.