In this special case I'm gonna try to rewrite the test case as an 
excercise - it doesn't seem like that much extra work, and I'd rewrite 
it anyway I'm not satisfied with it's current form even if it was to stay in Java.

But this is just postponing of this important question.

As much as I don't like the idea of mixing in the Java code to now still 
(almost) pure scala modules - maybe just an aesthetic preference of mine.

I'd like to have an oportunity to add a Java test if it's something more 
complex in the future. - in cases where advantages and quickness of 
availability of java unit test outweigh the unniceness of the mixing.

So +1 for allowing java test cases in scala modules