#include<bits/stdc++.h>
#define il inline
using namespace std;
const int maxn=200010;
il int read(){
	int x=0;
	char c=getchar();
	for(;!(c>='0'&&c<='9');c=getchar());
	for(;c>='0'&&c<='9';c=getchar())
		x=(x<<1)+(x<<3)+c-'0';
	return x;
}
struct edge{
	int v,to;
}e[maxn<<1];
int head[maxn],ecnt;
void addedge(int u,int v){
	e[++ecnt].v=v,e[ecnt].to=head[u],head[u]=ecnt;
}
int T,n,f[maxn];
void dfs(int fa,int x){
	int Mx=0,cMx=0;
	for(int i=head[x];i;i=e[i].to)
		if(e[i].v^fa){
			dfs(x,e[i].v);
			if(f[e[i].v]>Mx) cMx=Mx,Mx=f[e[i].v];
			else if(f[e[i].v]>cMx) cMx=f[e[i].v];
		}
	f[x]=max(Mx,cMx+1);
}
void clear(){
	for(int i=1;i<=n;i++) f[i]=head[i]=0; ecnt=0;
}
int main(){
	T=read();
	while(T--){
		clear();
		n=read();
		for(int i=1,x;i<=n;i++){
			x=read();
			if(x) addedge(x,i),addedge(i,x);
		}dfs(0,1),printf("%d\n",f[1]);
	}
	return 0;
}