I created a Python program to generate SVG test pattern files to find the best speed / power settings needed to cut different materials. It generates a matrix of squares with associated text. The text is vector so it can be scored instead of engraved to make the cut time quicker. Each test cutout is a different color so you can set its speed and power individually. Requires Python and a bit of Python knowledge to run. Get it from Github here.
Edit: Since you get to specify the values of speed & power to test, this program makes a custom test file that lets you home in on the optimal settings quickly. I wanted more targeted test files than the generic ones available elsewhere.