#include <bits/stdc++.h>

#define ll long long
using namespace std;
int n;
int fa[200010];

class node {
public:
    int v, next;
} edge[400020];

int head[200010], cnt;

void add(int u, int v) {
    edge[++cnt].v = v;
    edge[cnt].next = head[u];
    head[u] = cnt;
}
int f(int x) {
    vector<int>r;
    for(int i = head[x];i;i = edge[i].next) {
        r.push_back(f(edge[i].v));
    }
    if(r.empty())return 1;
    if(r.size() == 1)return max(1,r.front());
    sort(r.begin(),r.end());
    return max(r.back() - 1,r.end()[-2]+1);
}
int main() {
//    ios::sync_with_stdio(0);
//    cin.tie(0);
//    cout.tie(0);
    cin.tie(0)->sync_with_stdio(0);cout.tie(0);
    int t;
    cin >> t;
    while (t--) {
        cin >> n;
        cnt = 0;
        memset(head, 0, sizeof(int) * (n + 2));
        for (int i = 1; i <= n; i++) {
            cin >> fa[i];
            add(fa[i], i);
        }
        cout<<f(0)<<"\n";///<<" "<<f(1)<<" "<<f(2)<<" "<<f(3);
    }
    return 0;
}