Bug(?) when running test suite

[joshniemela]

Running the test suite with cargo test resulted in these two following errors whilst trying to acquire a lock on the model cache.

Running suite a second time resulted in no errors, which makes me believe this might be a race condition on how models are cached.

[l1x]

I think the values were copied and not calculated and this breaks the test, unless I am totally misguided.

Addressing it here: #204

[joshniemela]

@l1x your fix addresses that the test itself also has wrong values, I encountered this after running the test suite again for one of my own PRs.
The issue I'm reporting here is specifically about some strange race condition where the tests fail due to lock contention on the cache.

[lmmx]

Yeah I saw this too FYI