I do have some lab resources available to me for standing up and tearing down VMs of various OS flavors.
The resources are not limitless, but more than I have on my personal machines.
We've been using puppet and ansible for some of our internal test automation. One or both may be candidates for automated testing of BackupPC.
The way work allows me to spend time on Open Source projects is to work on issues reported to some form of bug tracker, so as long as there is an open issue that I feel I can tackle, I can try to get time to work on it in our next sprint. If you want to create an issue in github, I'll include it in our next sprint planning meeting.
As a little background, I've been using BackupPC for probably 9 years or more, personally and professionally, with Linux and Windows clients and am excited that the project is going to continue to grow and develop!
-Rich