Creating a Jar of test binaries - Gradle

I'm using the latest version of Gradle (milestone 9), and I'm trying to figure out how to create a Jar of all test binaries. From what I've found on the internet, the following should work: ``` task packageTests(type: Jar) { from sourceSets.test.classes } ``` However I am getting a - Cannot get the value of write-only property 'classes' on source set test. What is the correct way of coding what I'm trying to achieve? Is the property 'classes' somehow deprecated now ?