fedup is the old boring, dnf system upgrade is the new shiny - we need to switch over the upgrade tests. I'm working on this now and have something that pretty much works, but it seems to hit a bug in the upgrade process, looking into that now.
This ticket had assigned some Differential requests: D567
D567 handles this.
This is all done now.
This issue has been migrated to Fedora Forge: https://forge.fedoraproject.org/quality/os-autoinst-distri-fedora/issues/20
Please continue any further discussion there.