This a pretty traditional Gatsby site. You can start it up via:
yarn startWhich starts up a dev server.
Right now one of the main ways in which the site is tested is via visual regression testing using BackstopJS. Currently this is directly tied to Orta's computers and set-up so it isn't feasible for others to run them.
To run them from this folder:
# install globally
# npm install -g backstopjs
# To run the tests
backstop test
# To agree to changes
backstop approve