This would make life considerably easier, especially given there is a typo in the gradle-users thread that refers to this feature that took me a couple of hours to find.

task test(overwrite: true, dependsOn: classes) << {

should have been

task test(overwrite: true, dependsOn: testClasses) << {

otherwise running the test task won't compile your tests first.

I would suggest

test << {
    ant.taskdef(name: 'scalatest', classname: 'org.scalatest.tools.ScalaTestAntTask', classpath: classpath.asPath)
    ant.scalatest(runpath: testClassesDir, haltonfailure: 'true', fork: 'false') {
        reporter(type: 'stdout')
    }
}

... in order to keep properties of the Task object configured by Gradle. Thus we can get use of convenience properties testClassesDir and classpath, for example. More over overwriting task "test" disables integration with other testing frameworks.

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Thanks again for reporting this issue. We haven't heard back from you after our inquiry from November 15th. We are closing this issue now. Please create an issue on GitHub if you still feel passionate about getting it resolved.