Scotland went down 18-3 to the Springboks in Marseille in the pool stages of last year's Rugby World Cup but Dempsey sees Sunday's match as a chance to show just how much progress the Scots have made since.
"I'm itching for it," said Dempsey. "It's the ultimate test.
"They're the back-to-back defending champions, the best in the world. And they deserve to have that crown. They're the ultimate litmus test in terms of being a professional rugby player.
"We're at a point now where we want to see how much we've grown from the World Cup, from when we played them last time. They're the best country for eight years straight.
"We're not under any illusion about what's coming, but we're glad to have them here and glad to play against the best in the world."
Dempsey has won 20 caps since switching allegiance from Australia to make his debut for Gregor Townsend's team two years ago.
"Yeah, I've loved it," said the Glasgow back-rower. "Two years already, it feels a lot longer. There have been ups and downs like anything, but I've loved every second of it. I said at the time to get that second chance in the Test arena was a dream come true again.
"But to fast-forward two years and the bonds I've created, some of the friends I've made, the experiences while I've been over here have been unreal.
"It's just kind of been a match made in heaven with the style Gregor wants to play, with the history and the kind of identity that Scotland have always kind of had and played with."