It doesn't go to that page for me.
Yesterday I clicked it and it went nowhere.
Now I click and it goes to something that looks a lot like active conversations, but it only has the stickied threads and no other threads.
test.gransnet.com is a subdomain of gransnet. In the same way that mail.google.com or calendar.google.com all belong to google.com, ANTHING.gransnet.com belongs to gransnet.com
So I highly doubt it's dodgy, just perhaps not intended to be publicly viewable.
I'd imagine it's something like a staging server where changes are tested before being rolled out fully.