Add some tests

[bkazi]

Is currently just a POC
but sooner or later it will require some testing
What are the available testing options? (Jest, Mocha, etc.)
What can/needs to be tested specifically? (probably the single most important and difficult question)

[bkazi]

I've added 'some' tests along with the basic framework for testing etc, now it's more of getting coverage up and writing sane tests that test functionality usefully

(look at #5 and #6 for more on the testing saga)