cxtest's run.sh script has a --no-vnc option. I know I have once run a test outside of VNC so VNC is not a hard requirement. cxtest will probably complain about it though, and you might lose some functionality like automatic screenshots on failures. The best would be to try it out.
--no-vnc works fine for me for playing tests, but it does not work for recording tests. Thats pretty bad because the vnc server does not even have opengl, not even a software renderer. Because of that the benchmarks refuse to start up at all. I tried to write the test scripts manually(I don't need many clicks after all), but finding out all the button IDs sounds bad :-/ I'll try my luck with keystrokes now...