#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]);
		for (int i = 1; i <= n; i++) vec[i].clear();
	}
	return 0;
}
/*
2
3
0 1 2
7
0 1 2 2 1 4 1
*/

answer.code: In function ‘int main()’:
answer.code:33:46: error: ‘vec’ was not declared in this scope
   33 |                 for (int i = 1; i <= n; i++) vec[i].clear();
      |                                              ^~~
answer.code:23:14: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   23 |         scanf("%d", &T);
      |         ~~~~~^~~~~~~~~~
answer.code:25:22: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   25 |                 scanf("%d", &n);
      |                 ~~~~~^~~~~~~~~~
answer.code:28:30: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   28 |                         scanf("%d", &x);
      |                         ~~~~~^~~~~~~~~~