Yes, I tried further, the JS random tests sometimes generate inputs like:
([3, 3], "1,3 2")
where N == M, and expect null, even though nothing seems to contradict the specifications here: there are N unique numbers between 1 and M, separated by spaces and/or a comma

After a couple attempts I managed to submit, this is likely a kata issue

was this test a random one ?

given [n, m]

n the expected length

m the maximum value

to me the string is valid

JavaScript:

[7,7], "2   5 6  1, 7 , 3 4" -> null
Expected: null, instead got: [1, 2, 3, 4, 5, 6, 7]

what makes the string invalid here ?

Who can describe me what with that sequence is not OK? -(-_-)
Test Failed
Expected: null
But was: < 4, 5, 10, 32, 35, 42 >