Infinitest is an eclipse plugin which executes after editing files all corresponding unittests. After using infinitest for a while I realize that some features of TestNG 6.8 are not available by infinitest itself (in my case assertNotEquals). And therefor result in a reported problem.
Fortunately the project is availible on github and so I fork the project and change it to support TestNG 6.8. An pull request to the original project is waiting.
If you want to try it on your own risk - you can download it here. To install it in your Eclipse you have to unzip the file in the eclipse/dropins directory. I have test the version on Win7 and OSX with Eclipse 3.7 - and it seems to work ;-)