stan-dev/stan — pull request #341 by betanalpha (2013-10-29 10:27:00+00:00)
Title: Feature/more hmc tests

Let it be said that the HMC code is tested to the nines.

Added tests for Hamiltonian derivatives as well as energy conservation and symplecticness of integrators (the latter using a cute algorithm that approximates volumes using the divergence theorem -- our tests are geometric now, too).