#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll INF = 0x3f3f3f3f3f3f3f3f;
typedef multiset<ll>::iterator itt;
const int N = 5e5+11, P = 998244353;

int n;
ll f[N], ans;
int tot, head[N], ver[N], nex[N];

void add(int x, int y){
	nex[++tot] = head[x];
	head[x] = tot;
	ver[tot] = y;
}

void dfs(int x, int fa){
	ll cnt = 0;
	for(int i=head[x]; i; i=nex[i]) if(ver[i] != fa){
		int y = ver[i];
		cnt ++; dfs(y, x);
	} if(!cnt) {f[x] = 0; return ;} 
	
	
	for(int i=head[x]; i; i=nex[i]) if(ver[i] != fa){
		f[x] = max(f[x], max(1ll, f[ver[i]]) + cnt - 1);
	} ans = max(ans, f[x] + (fa ? 1 : 0));
	
	if(cnt < 2) return;
	ll q[cnt+11], t = 0;
	for(int i=head[x]; i; i=nex[i]) if(ver[i] != fa){
		q[t++] = f[ver[i]];
	}
	sort(q, q + t);
	ans = max(ans, q[t-1] + q[t-2] + cnt - 2 + (fa ? 1 : 0));
}

void work(){
	scanf("%d",&n);
	tot = 0, ans = 1;
	for(int i=1;i<=n;i++) f[i] = head[i] = 0;
	for(int x,y,i=1;i<n;i++) scanf("%d%d",&x,&y), add(x, y), add(y, x);
	dfs(1, 0); 
//	printf("ans=%lld\n",ans);
	printf("%lld\n",ans);	
}

int main(){
	int t = 1; scanf("%d",&t);
	while(t--) work(); return 0;
}