Edit: I finally got it to work!!!
It needed a combination of JUnit in the pom.xml, and three statements in my .scala:
import org.junit.runner.RunWith
If you're running on Maven, then you'll either have to annotate your test class(es) with
@RunWith(classOf[JUnitRunner])
This would require you having JUnit as a dependency. Or you could use the ScalaTest Maven Plugin (haven't used it myself though).