can be tested locally. A QR code pops up on the developer's tool and can be paid by scanning the code. The client has a callback after payment.
the server callback address is passed by itself in the unified order issuing API, and can be called back to the local development computer using private network interpenetration.
the specific condition is that the official account that needs to be bound has already opened WeChat Pay. It seems that the callback address does not need to be set in the backend of WeChat Pay merchants.
I just got through yesterday. It must be no problem.

payment cannot be debugged locally, and a secure domain name must be set for payment, so payment testing can only be carried out when it is published online.