Unit testing with Node.js?

Currently, our unit testing is happening through PhantomJS, but I want to make sure we can work with node.js as well (i.e., not on a headless browser). I'm 90% sure we're not doing anything at this point that would prevent anyone from using this server-side, but just to make sure, let's explore options for server-side unit testing, preferably without rewriting all the tests.
