I've tried to use the one from Spotkiller, but it didn't work out at all for me (misalignment). So I created a new one from scratch.

Just drop into your preferred slicer and hit run. It prints only 1 layer. Added now other forms and a version for regular bed sizes so it's now usable for various printers.

Print time: approx. 08:30 min.

Update 2 (12/2017):

• Added test for other printer with bed sizes up to 200 mm
• Added round level test incl. single one
• Added a circle level test with 4 rings and a text object. You can check for bed adhesion and your quality settings with this too.

Update 1 (11/2017):

• Added a single square so you can place them by yourself.

Images:

• 01 Overview
• 02 Nozzle too close
• 03 Perfect
• 04 Nozzle too high
• 05 Perfect