I have started the openhab-js-helper as a private openHAB JavaScript helper
library to improve the quality of my JavaScript (ECMAScript 2022+) automation
rules. The library uses the yarn package manager for testing and building.
It also comes with a test suite using Jest. Jest not only let you test your
code, but also has an integrated mocking that I use to mock openHAB specific
objects.
In this way the code can be developed, tested and build outside an openHAB instance.