Kennedy, product testing and app testing are real jobs.
But how would a real client go about it?
A real client would hire you using an hourly contract.
You would log your time while downloading the app and writing about your experience while using it.
The client would provide you with a credit card number or bank account number that you would enter for "your" payment method. These would be test account numbers or sandbox numbers specifically set up for product testing purposes. You would not be asked to use your own financial account(s).
Did the client who hired you do these things, as I described?
If so, then this was not a scammer.
