To install dependencies for the tests, run npm install from the installation directory.
You will also need babel@cli version 7 or higher installed globally. The tests use babel-node to avoid having to run through a build step first, for convenience. Obviously this isn't great for performance, but I'm assuming for the puproses of the exercise that this aspect of performance can be overlooked.
The tests also assume a node version of 8.12.0 or greater.
In order to run the individual scripts, from the command line (in the install directory):
npm run-script simplenpm run-script mediumnpm run-script complex