The phrase "a confirmation of that" is correct and usable in written English.
It can be used when referring to the act of verifying or affirming something previously mentioned or discussed.
Example: "I will need a confirmation of that before proceeding with the project."
Alternatives: "verification of that" or "affirmation of that".
Today brought two statements out of Apple that are just about as close as you're ever going to get to a confirmation of that.
Last week, when we reported on the deal between Fair and Uber — which will also see Fair become Uber's exclusive leasing partner, initially in the US, for drivers on its service who are looking for a new car to drive — we got wind that the company had raised another round, and this is a confirmation of that.
Last night was just a confirmation of that.
This is a confirmation of that".
It took a bit of time and effort to facilitate that mental shift, but President Barack Obama's early visit to Turkey was a confirmation of that perception.
Esterly needed a confirmation of that diagnosis, so she carried the sample upstairs to the top floor, where William L. Nyhan, a pediatrician and research scientist, had a laboratory.
Update: Apple has issued a confirmation, of sorts, that it has purchased Novauris, telling TechCrunch that "Apple buys smaller technology companies from time to time, and we generally do not discuss our purpose or plans".
We don't quite know why until the very end of the novel, which comes both as a surprise and a confirmation of all that's gone before.
Still, the official forecast of an upturn in prices, however tiny, offered a confirmation of sorts that Japan was nearing the end of one of its most nagging economic problems.
In a confirmation of reports that she was gravely ill, Maxine Postal, one of the highest-ranking elected officials in Suffolk County, has announced she will resign from the County Legislature effective on Wednesday because of failing health.
This is a devastating confirmation of that".
