Handle missing serial numbers

[alexford]

After the discussion in #41 I figured I'd push up what I did to work around nodes without serial numbers available. I factored out that serial number retrieval into its own function.

Separately, I added a Jest test to help cover that case.

I realize choosing and adding Jest is a rather large suggestion/change. I'm happy to revert that if you'd rather not take that step, or use a different framework, etc. It was just a lot quicker to make sure this behaves as I expected by writing tests versus poking at real Z-Wave devices.

[mike182uk]

Hey @alexford

Sorry for the late reply, i completely missed this 🙈

Would you mind fixing the lint error and resolving the merge conflicts? Its probably easiest to pull in the package.json changes from master and running npm i to regenerate the package-lock.json rather than trying to resolve its conflicts manually 😃

I realize choosing and adding Jest is a rather large suggestion/change. I'm happy to revert that if you'd rather not take that step, or use a different framework, etc. It was just a lot quicker to make sure this behaves as I expected by writing tests versus poking at real Z-Wave devices.

Thanks for the taking the time to add this, its definitely something I should of got round to sooner rather than later. More than happy to keep it in 👍

[alexford]

I've rebased and fixed the lint error. Tried to get the tests to run on CI but openzwave doesn't seem fully happy on Travis (https://travis-ci.org/github/mike182uk/homebridge-zwave/builds/726733400?utm_source=github_status&utm_medium=notification)

[mike182uk]

Ah maybe we need to add a jest config file and tell it to only run tests in the lib dir?