I think there's an issue with the Kotlin version of this kata. Even when I implement the function in the most simple (not correct) way possible:

fun grow(arr: IntArray): Int = 6

I get this error from tests:

fixture.kt:10:25: error: unresolved reference: grow
        assertEquals(6, grow(intArrayOf(1, 2, 3)))

I can't submit the kata because of this, so this really should be resolved.

Great kata. Published C# translation (I'm quite new to the site so I hope I did it correctly).