I definitely want to, but I've not used jest before, so I'll be a bit slower than I'd be with mocha+chai. Where did you get your snapshots for the existing test? Would be nice to find an iOS or Android harmonic spring and assert that we get similar values out when we put similar ones in.
Re snapshots for the existing test -- I took them using the jest snapshot API (.matchSnapshot). It's basically just a regression test -- we're assuming the values that are currently in the snapshot are actually correct.
I agree about matching against the ios spring -- but that's going to be pretty hard. I'd have to go through frame-by-frame and dump the memory registers :)