agreed. it would be fine if you didnt have to account for null or empty arrays.

Lol I came here to say the same thing. This was a lot harder than every other 8ku I've done so far.

I suggest to include (Rust language) this test in order to check non empty vector when all elements are zero (see my last exercise attempt to understand the reason):

#[test]
fn all_zeroes_not_empty_result() {
    assert_eq!(count_positives_sum_negatives(vec![0]), vec![0, 0]);
    assert_eq!(count_positives_sum_negatives(vec![0, 0, 0, 0]), vec![0, 0]);
}

Not a kata issue, that's a problem with your code:

If the input is an empty array or is null, return an empty array.

can't be changed ^^