Gradle play plugins custom test scala directory

How to specify custom test scala directory when using play plugins?

our source and test code location are:

src/main/scala
src/test/scala

specify source is easy according to the documentation:

model {
    components {
       play {
          sources {
              scala {
                 source.srcDir "src/main/scala"
             }
        }
   }
...

How to specify the test source directory? Any help will be greatly appreciated.

can someone help? It seems to be a pretty basic requirement/bugs