That's correct, you set it up with a mock database, and npm test inserts its own testing data and cleans up after itself when it's done. No need to have NodeBB running for the testing suite to run.
NPM Audit vulnerabilities
Just noticed few vulnerabilities flagged by npm audit.
It may make sense to update less, debug (socket.io-adapter-mongo), and string.
Not sure however if updating these libraries break other code.
Thank you @julian , that's awesome!