I'm also looking for testers for my app Money Forecast — a personal finance app for tracking expenses and forecasting your future balance. Works 100% offline.
Since it's a paid app, the process is slightly different:
Join the Google Group: https://groups.google.com/g/moneyforecast-testers
Let me know your email so I can confirm you're added, and join email in testers.
Then access the beta: https://play.google.com/apps/testing/com.nunorfo.moneyforecast
To download you press in price, in the next screen will show you can download without paying