Hi, I realise I am very late to this thread, but I thought I'd chip in with a bit of info that caught out a Gradle newbie (i.e. me).
There is a slight typo in Adam's test task that means the task doesn't compile test classes beforehand. I think task test(overwrite: true, dependsOn: classes) should have read task test(overwrite: true, dependsOn: testClasses). I've written a blog post about getting Gradle and ScalaTest to play nicely together <http://martingladdish.co.uk/index.php?option=com_content&view=article&id=69:getting-into-scala-and-gradle&catid=34:code>, and added my vote to the Jira issue <http://jira.codehaus.org/browse/GRADLE-1032> raised. Thanks, Martin Gladdish.