Three tests carried the maintainer's production root domain, a personal
mailbox and the public IP of a live demo host as fixture values. None of
them needs the value to be real: the re-domain test only needs two
different roots, and the setup flow only needs a well-formed address.
Swap them for the placeholders the rest of the suite already uses
(mc.example.net, [email protected]), and move the "before" root in the
re-domain test to 203.0.113.10.nip.io. That address is from the RFC 5737
documentation range, so the stale install the test models still has an
IP-derived hostname, which is the case the refresh exists for.