How to Write Tests For Android App For File Transfer and QR Code Confirmation B/w Two Devices

I want to write tests for an android app that transfers files b/w two devices using hotspot/QR Code. To connect those two devices a hotspot connection is required. The process works like this:

• In order to send something, Device A generates a QR Code and it's hotspot is turned on and on the same page a port no is written.

• The device on the receiving end has two ways to receive the file.

1) It should connect to Device A's hotspot. After that it will have to write the port no that was shown on Device A's screen with the hotspot.

2) It should scan the QR Code that is shown on Device A's screen.

These tests should work on emulator because I can't physically own all Android version devices.

I need to write tests for this app's functionality.

1- To confirm QR Code has been generate and then verified.

2- To confirm files are transferred/received successfully.

3- To confirm the hotspot service

Here's the app documentation to read more about it. GIFs are also available showing how this app works.