No, this is a real miniatures game. It's an insanely good one at that. A skirmish level game with tons of fan support, playtesting and a living community, "This is Not a Test" (TNT) combines elements of many classic iterations of the post-apocalyptic adventure setting. Heavily influence by Fallout it is much more than that and you can find nods to Road Warrior, horror movies, even classics like Gamma World.
While written with 28mm in mind, TNT works perfectly well for 15mm and other scales. You can successfully play it in 15mm without even adjusting ranges, the distances will just seem a bit more real scale. The game has its own growing range of 28mm miniatures but the rules showcase a range of miniatures from several manufacturers proving that this game will allow you to get started with many of the miniatures already in your collection.