#include <iostream>
using namespace std;
int par[200'007];
int nch[200'007];
int mav[200'007];
int cnt[200'007];
void solve(){
    int n; cin >> n;
    fill_n(nch, n, 0);
    fill_n(cnt, n, 0);
    fill_n(mav, n, 0);
    fill_n(cnt, n, 0);
    for (int i = 0; i < n; i++){
        int p; cin >> p;
        par[i] = p - 1;
        if (p > 0)
            nch[p-1]++;
    }

    for (int i = 0; i < n; i++){
        int j = i;
        while (j >= 0 && nch[j] == 0){
            if (cnt[j] > 1)
                mav[j]++;
            int p = par[j];
            if (mav[p] > mav[j]){
                mav[p] = mav[j];
                cnt[p] = 1;
            }
            else if (mav[p] == mav[j]) cnt[p] = 2;

            j = par[j];
            nch[j]--;
        }
    }
    if (n == -1)
        cout << "0\n";
    else
        cout << mav[0] + 1 << "\n";
}
int main(void){
    ios::sync_with_stdio(0); cin.tie(0);
    int t; cin >> t;
    while (t--) solve();
}