Artifact is a case study in how user testing alone goes wrong.
They did extensively test Artifact but user testing will get you stuck in local maxima. You still need someone with a good wholistic vision to make a great product.
I heard they had a lot of feedback along the lines of "I really like this game, but I'm not sure if other people will" (this from a friend who is friends with one of the artifact devs, so take it with a healthy dose of salt).
I support wholistic as an alternate spelling of holistic. You're actually likely to come to a good idea of what it means even if you've had no exposure to real word before.
They did extensively test Artifact but user testing will get you stuck in local maxima. You still need someone with a good wholistic vision to make a great product.