#include<bits/stdc++.h>
using namespace std;
#define int long long
#define debug(x) cerr<<#x<<' '<<x<<' ';
typedef pair<int, int>PII;
typedef long long LL;
constexpr int N = 200010, mod = 1e9 + 7;
int a[N];
vector<int>v[N];
int cnt[N];
void dfs(int u, int fa)
{
    int f = 0, ma = 0;
    int d1 = 0, d2 = 0;
    for(auto c : v[u])
    {
        if(c == fa)continue;
        f++;
        dfs(c, u);
        if(cnt[c] > d1)
        {
            d2 = d1;
            d1 = cnt[c];
        }
        else if(cnt[c] > d2)d2 = cnt[c];

    }
    if(d2 + 1 >= d1)cnt[u] = d2 + 1;
    else
        cnt[u] = d1;
}
signed main()
{
    //freopen(".in","r",stdin);freopen(".out","w",stdout);
    ios::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);
    int t;
    cin >> t;
    while(t--)
    {
        int n;
        cin >> n;
        for(int i = 0; i <= n; i++)v[i].clear(), cnt[i] = 0;
        for(int i = 1; i <= n; i++)
        {
            int x ;
            cin >> x;
            v[x].push_back(i);
        }
        dfs(1, 0);
        cout << cnt[1] << endl;
    }

}