Simple, clean and fast test cube. I will give credit to whomever I nicked this idea from (I can't find him/her/them in my history) - I think I left you a comment so let me know and I'll thank you again - plus I've lost you mate. 

This cube Helps me to very quick speed and quality tests when trying out new filament. There's no overhang just a couple of extrusions variants,  a couple of Boolean carves and a few nice flat surfaces. 

I've also uploaded a 20mm test slab for top surface tuning.

https://makerworld.com/en/models/813261#profileId-755071