But everyone pretty much tests the same lists for each format, with some minor tweaks. The tests become a self-fulfilling prophecy because you only test the songs that you already know test well.
There are exceptions to this... I know Cary Pall occasionally posts here, and I think he researched something like 2,000 titles when they originally put WMMO/Orlando on the air. It was a really unique music-oriented AC that played stuff that you absolutely couldn't hear anywhere else, and it did very well for a few years. Eventually Cox bought it and distilled it down to 300 songs and now it's just another boring AC station.