Add unit tests

[simlu]

Things are getting pretty complicated and I vote for adding unit tests... should make everything a lot cleaner.

The way that I see this:
(1) have a joi schema
(2) generate the json schema
(3) check that the joi and json schema both validate / fail to validate certain data

[kenspirit]

@simlu I admit that more test cases and scenarios should be covered.

The current test is also trying to make all kinds of different cases into a big complex joi schema for every version and come up with a universal json schema to check against.

Your supplemented scenarios are very helpful as I could not think out all possible scenarios.

Will try to add more and thanks as always.