Implement Jest about threeify

[pailhead]

Investigation

• It seems the config needed is fairly minimal, but it requires babel.
• i think there's choice when it comes to structuring the test files, they can be next to the source or in /__test__/

[pailhead]

@bhouston Please assign this to me.

[bhouston]

Sorry, I missed that you wanted me to assign it to you. I will track these issues a bit closer going forward.

[bhouston]

I notice a discussion here that seems to suggest that Jest is it. It is actually used by React-Create-App.

i can likely port across a lot of the math tests from Three.js relatively quickly: https://github.com/mrdoob/three.js/tree/dev/test/unit/src/math

[bhouston]

I do not care if it is in test or beside the code. Go with whatever you feel is best for now and we can change it in the future if needed.