How do I run the drush tests in docker?

I'm trying to improve drush, and the drush contributing guidelines state:

Drush's own tests may be run within provided Docker containers (see docker-compose.yml):

Start containers: docker-compose up -d

So I forked Drush on Github, cloned the repo locally, and then, from the repo root, ran docker-composer up -d. This gives an error:

ERROR: Can't find a suitable configuration file in this directory or any parent. Are you in the right directory?

So then I tried to find the right directory by searching for a docker-compose.yml, but I can't find it anywhere. I searched the Drush repo on GitHub as well but I couldn't find it there, either.

How do I launch docker-compose to run the drush tests?