When testing creatives on Facebook, should you test all creatives within a single ad set, or give each its own ad set?

I always test within a single ad set -- this allows Facebook to tell you which ads perform best via its budget allocation deliberation.

Although, thinking about this, I suppose you would achieve the same thing by splitting the creatives out into their own ad sets, assuming the campaign was running CBO. But that's more work.

I also put the test ad sets in a wholly separate campaign / ad account so that their performance doesn't impact delivery on live, scaled ad sets.

we prefer to test within a single ad set -> so underperforming ads dont get a ton of spend and result in wasted spend.

if you test in separate ad sets, each ad set(and hence ad) ends up with non-trivial amounts of spend.

that said, we do know of advertisers who have more leeway with testing budgets that run creative tests in separate ad sets.