Hi!
First, thanks for this kata.

What about to modify this kata and instead of (n x n) size array, provide with (n x k) size array

(would be more challanging :) )

Nice kata. Thanks

Challenging.
Done.
Thank you!

add public to class Reflections{}

And small pain again :))
Thank you! Got pleasure
Sorry for my ugly code :)

Thank you for the pain:))
Was interesting!

This is a pain

Thanks! Empty string was confusing to me.

Code return value (Empty string) should not be ("") and not ("":"") it should be exactly what author indicated - only ""

My solution is passed almost all tests in R version, but generates error at the end:

Test Failed

non-character argument
 1: testing(b, c, res) at tests.R:30
   2: stockList(listOfArt, listOfCat) at tests.R:2
   3: strsplit(listOfArt, split = " ")

Need help to figure out what it means.

And it is not clear in case of (listOfCat) has "" empty element.
I suppose code should not return anything in case "" empty element.