#include<iostream>
#include<algorithm>
#include<vector>
using namespace std;
const int max_n = 1e5+100;
vector<int> G[max_n];
vector<int> v1,v2,v3,v4;
int n;

int dfs(int u,int p)
{
	int du=0;int net = u;
	for (int v:G[u])
	{
		if (v==p)continue;
		int re = dfs(v,u);
		if (re<0)continue;
		++du;
		if (du==1)net = re;
		else if (du==2)
		{
			v1.push_back(p);
			v2.push_back(u);
			v3.push_back(net);
			v4.push_back(re);
			net=-1;
		}
		else
		{
			v1.push_back(u);
			v2.push_back(v);
			v3.push_back(v);
			v4.push_back(re);
		}
	}
	return net;
}

int main()
{
	ios::sync_with_stdio(0);
	int t;cin>>t;
	while (t--)
	{
		cin>>n;
		for (int i=0;i<=n;++i)G[i].clear();
		v1.clear();v2.clear();v3.clear();v4.clear();
		for (int i=1,u,v;i<n;++i)
		{
			cin>>u>>v;
			G[u].push_back(v);
			G[v].push_back(u);
		}
		int to;
		for (int i=1;i<=n;++i)
		{
			if (G[i].size()==1)
			{
				to=dfs(i,-1);
				break;
			}
		}
		cout<<v1.size()<<endl;
		for (int i=0;i<v1.size();++i)
		{
			cout<<v1[i]<<" "<<v2[i]<<" "<<to<<" "<<v4[i]<<endl;
			to=v3[i];
		}
	}
}