Can I control an already built app, whose .apk file I have, using some other app?

[AC Question]

I need to automate the long registration process inside one already developed app. I don't have the source code for this app. So, I want to develop another app that controls the UI of the first app and auto populates the various details and clicks the buttons automatically, without user intervention. Something similar to what Appium and Selenium do with their automated test scripts, but in app form. Is this possible. Or can you provide me direction on how I should proceed with this?
Thanking in anticipation.

 

[AlphaTango414]

It is possible. However, I can not help you any further. Good luck.

 

[Rukbat]

Just develop an app that watches the screen and clicks/writes to the appropriate places. (It would be a lot easier to write the original app in an "automatic fill" version. Automating an app when all you have is the screen isn't easy.)