Owen Taylor of Red Hat has publicly announced gnome-battery-bench for Linux laptop battery testing.
Owen's blog post does a good job covering all of the basics for this new program. I've been communicating with Owen and Christian Schaller for the past month now over GNOME Battery Bench and testing it out. The necessary support should be in place with this release for it to be able to be run automatically for benchmarking with the Phoronix Test Suite -- sans the matter of manually needing to put the device into battery power mode by pulling the AC plug.
There's the README and Git repository for GNOME/Linux battery benchmarking.