#include <bits/stdc++.h>

#define maxn 200005

using namespace std;

int T;
int n;
int f[maxn];
vector<int> g[maxn];

void dfs(int u, int fa) {
	int mx = 0, cm = -1;
	for (int v : g[u]) {
		dfs(v, u);
		if (f[v] >= mx) cm = mx, mx = f[v];
		else if (f[v] >= cm) cm = f[v];
	}
	f[u] = max(mx, cm + 1);
}

int main() {
	scanf("%d", &T);
	while (T--) {
		scanf("%d", &n);
		for (int i = 1; i <= n; i++) {
			int x;
			scanf("%d", &x);
			if (x) g[x].push_back(i);
		}
		dfs(1, 0);
		printf("%d\n", f[1]);
	}
	return 0;
}
/*
2
3
0 1 2
7
0 1 2 2 1 4 1
*/