Why, oh why, doesn’t TestNG work for me?

I switched several projects from JUnit 3 to TestNG. After some minor problems with the fact that TestNG doesn't seperate tests as JUnit does per default, everything works in IDEA and Maven. But whatever I tried, I can't get TestNG to work with Ant. The TestNG Ant task just doesn't find any tests. I used testjar, dir, includes and it also doesn't help that the TestNG documentation is sparse and misleading. I moved Messages to TestNG too, but without Ant support this will not be released. Everything works fine, just Ant doesn't. If I can't get it working, I'll give Junit 4 a try.