A very small "cube" print that I use to test printers rapidly. Definitely doesn't test much, but it can at least verify the extruder is working properly, or that the hotend heats up.

Sliced at .2mm layer thickness, this takes approximately 15 minutes on my Ender 3.

Meant for speed and rapid-iteration testing, not fine details.

Post-print, part dimensions should be as follows:

Base: 20.0mm by 20.0mm.
Height: 10.0mm.
The little post in the corner should be 1.00mm thick.
Diameter of the circle: 6.00mm.

You can get a rough idea of stringing from the corner post across the gap in the walls, and a rough idea of print head movement from the circle in the center.