#include<bits/stdc++.h>
#pragma GCC optimize("O3,unroll-loops,fast-math,no-stack-protector")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
using namespace std;
const int N=200005;
struct edge{int v,nxt;}e[N<<1];
int T,tp,id[N],deg[N],mx[N],mn[N],n,m,h[N],cnt,rt,ban[N],u,v;
void add(int u,int v){e[++cnt]={v,h[u]};h[u]=cnt;}
void dfs(int u,int fa)
{
	if(deg[u]==1)id[m]=u,mn[u]=mx[u]=m++;
	else mn[u]=0x3f3f3f3f,mx[u]=-0x3f3f3f3f;
	for(int i=h[u];i;i=e[i].nxt)
	{
		int v=e[i].v;
		if(v==fa)continue;
		dfs(v,u);
		mn[u]=min(mn[u],mn[v]);mx[u]=max(mx[u],mx[v]);
	}
}
namespace Sub0
{
	void main()
	{
		for(int i=1;i<=n;i++)
		{
			if(i==rt||deg[i]==2||(mx[i]-mn[i]+1)%2==1)continue;
			ban[(mn[i]+mx[i]+1)/2%(m/2)]++;
		}
		for(int x=0;x<m/2;x++)
		{
			if(ban[x]==0)
			{
				int a=x,b=(x-1+m)%m;
				for(int i=1;i<=m/2;i++)
				{
					cout<<id[a]<<' '<<id[b]<<'\n';
					a=(a+1)%m;b=(b-1+m)%m;
				}
				cout<<1<<' '<<1<<'\n';return;
			}
			else if(ban[x]==1)
			{
				int l=-1,r=-1;
				for(int i=1;i<=n;i++)
				{
					if(i==rt||deg[i]==2||(mx[i]-mn[i]+1)%2==1)continue;
					if((mn[i]+mx[i]+1)/2%(m/2)==x)l=mn[i],r=mx[i];
				}
				int A=r-l+1;int B=m-A,a=x,b=(x-1+m)%m;
				for(int i=1;i<=m/2;i++)
				{
					cout<<id[a]<<" "<<id[b]<<'\n';
					if(l<=a&&a<=r)A--;
					else B--;
					if(l<=b&&b<=r)A--;
					else B--;
					if(A==0||B==0)cout<<id[r]<<' '<<id[(r+1)%m]<<'\n',A=-1,B=-1;
					a=(a+1)%m;b=(b-1+m)%m;
				}
				if(A==0||B==0)cout<<id[r]<<' '<<id[(r+1)%m]<<'\n',A=-1,B=-1;
				return;
			}
		}
	}
}
namespace Sub1
{
	void main()
	{
		for(int i=1;i<=n;i++)
		{
			if(i==rt||deg[i]==2)continue;
			if((mx[i]-mn[i]+1)%2==0)ban[(mx[i]+mn[i]+1)/2%(m/2)]++;
			else ban[(mx[i]+mn[i]+1+m)/2%m]++;
		}
		for(int x=0;x<m;x++)
		{
			if(ban[x]==1)
			{
				int a=x,b=(x-1+m)%m;
				for(int i=1;i<=m/2;i++)
				{
					cout<<id[a]<<' '<<id[b]<<'\n';
					a=(a+1)%m;b=(b-1+m)%m;
				}
				cout<<id[(x+m/2)%m]<<' '<<id[(x+m/2+1)%m]<<'\n';
				return;
			}
		}
	}
}
int main()
{
    cin.tie(0)->sync_with_stdio(0);
    cin>>T;
    while(T--)
    {
    	cin>>n;
    	for(int i=0;i<=n;i++)deg[i]=h[i]=ban[i]=0;cnt=m=0;
    	for(int i=1;i<n;i++)
    	{
    		cin>>u>>v;
    		add(u,v);add(v,u);deg[u]++;deg[v]++;
		}
		int M=0;
		for(int i=1;i<=n;i++)M=max(M,deg[i]);
		if(n==2){cout<<"1 2\n1 2\n";continue;}rt=0;
		for(int i=1;i<=n;i++)if(deg[i]==M)rt=i;
		dfs(rt,0);
		if(m%2==0)Sub0::main();
		else Sub1::main();
	}
	return 0;
}