Gradle now uses separate output directories for each JVM language, but this build assumes a single directory for all classes from a source set. This behaviour has been deprecated and is scheduled to be removed in Gradle 5.
and
The setTestClassesDir(File) method has been deprecated and is scheduled to be removed in Gradle 5.0. Please use the setTestClassesDirs(FileCollection) method instead
using gaelyk plugin with gradle 4.0 gives
Gradle now uses separate output directories for each JVM language, but this build assumes a single directory for all classes from a source set. This behaviour has been deprecated and is scheduled to be removed in Gradle 5.
and
The setTestClassesDir(File) method has been deprecated and is scheduled to be removed in Gradle 5.0. Please use the setTestClassesDirs(FileCollection) method instead
probably should address this at some point
Thanks