We should check not only that the existing system for reuse is Fedora Linux but also that there are expected mount points (the default Fedora WS installation).

This check would make plain Fedora Cloud Image rawhide images unusable for testing as they have separate /var (unlike Fedora Workstation with just separate /home)

As first solution we can try to modify the image before the test but as long term solution it would be great to have images of Fedora WS default installations (of $CURRENT of $CURRENT-1 release) but I think this could be handled separately, with its own proper amount of Story points.