ABC F求条

// Problem: F - Centipede Graph
// Contest: AtCoder - AtCoder Beginner Contest 447
// Date: 2026-02-28 20:00:16
// URL: https://atcoder.jp/contests/abc447/tasks/abc447_f
// Memory Limit: 1024 MB
// Time Limit: 2000 ms
// Author: AnotherDream
// 
// Powered by CP Editor (https://cpeditor.org)

#include <bits/stdc++.h>
using namespace std;
#define fir first
#define sec second
#define debug cerr<<"The code runs successfully.\n";
#define endl '\n'
#define TRACE 1
#define tcout TRACE && cout
#define fst ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define int long long
const int P = 998244353; 
const int Base = 33331;
#ifdef int
const int INF = 0x3f3f3f3f3f3f3f3f;
#else
const int INF = 0x3f3f3f3f;
#endif
const int N = 2e5 + 10, M = 1e6 + 10;
vector<int> g[N];
int n,T,dp[N][2];
inline void dfs(int u,int f) {
	dp[u][0]=dp[u][1]=1;
	if(g[u].size()==3) {
		return;
	} 
	int ans1=0,ans2=0;
	for(int v:g[u]) {
		if(v!=f) {
			if(g[v].size()>=3) {
				dfs(v,u);
				dp[u][0]=max(dp[u][0],dp[v][0]+1);
				if(dp[v][0]>ans1) ans1=dp[v][0];
				else if(dp[v][0]>ans2) ans2=dp[v][0];
				dp[u][1]=max(dp[u][1],dp[v][1]);
			}
		}
	}
	dp[u][1]=max(dp[u][1],ans1+ans2+1);
	dp[u][1]=max(dp[u][1],dp[u][0]);
}
inline void solve() {
	cin>>n;
	for(int i=1;i<=n;i++) {
		g[i].clear();
		dp[i][0]=dp[i][1]=0;
	}
	for(int i=1;i<n;i++) {
		int u,v;
		cin>>u>>v;
		g[u].push_back(v);
		g[v].push_back(u);
	}
	for(int i=1;i<=n;i++) {
		if(g[i].size()>=4&&dp[i][0]==0) {
			dfs(i,0);
		}
	}
	int res=0;
	for(int i=1;i<=n;i++) {
		if(g[i].size()>=2) res=max(res,1ll);
		for(int v:g[i]) {
			if(g[v].size()>=3&&g[i].size()>=3) res=max(res,2ll);
		}
		res=max(res,dp[i][1]);
	}
	cout<<res<<endl;
	cerr<<endl;
}
signed main() {
	fst;
	cin>>T;
	while(T--) solve();
	return 0;
}