This was a theme created by Theme-Gen, a CLI utility that takes an existing theme and a starter site, and makes a new theme by copying the existing theme and applying small changes to it from what it can see on the starter site.
For example, if I have the blank-canvas theme and a https://fredricksonstarter.wordpress.com/ starter site that contains a homepage design with font and color settings, I can create a new fredrickson theme.
To create my-new-theme based on blank-canvas and fredricksonstarter.wordpress.com:
wp --require=wp-content/lib/theme-gen/init.php theme-gen fredricksonstarter.wordpress.com blank-canvas my-new-theme
To run unit tests:
cd ~/public_html/bin/tests/isolated && phpunit --testsuite=theme-gen