First, set up the session cookie file which will be used for fetching input. In the browser, copy the value of the session cookie for the site, which should be a long hex string, and save it in a file called session.cookie.
To run tests for all days:
npm test
To run tests for a specific day:
npm test -- -g 04
OR
npm test test/04.spec.js
To run the solution for a particular day:
bin/aoc 4
OR
npm start 4
To debug:
DEBUG=aoc bin/aoc 4