This is a simple model to help test the directional uniformity of your cooling fan air flow, and your fan speed settings.
I find the best indicator of poor cooling is curling corners on overhangs. So this model has pointed overhangs in the shape of an 8 pointed star, aligned to the x and y axes. The Orientation is labeled on top, so you don't loose track of which way around it was printed, after you remove it from the build plate.(Having your fan speed too high can lead to poor layer adhesion, so adjust it to the minimum speed which gives good overhang performance.)
In the photos, you'll see the effect of my printer's slightly weak air flow from the -Y direction.
The Fusion 360 file is parameterized, so you can edit the overhang angle and the amount of flare, just by changing the numbers.
Remember to disable supports.