// what is matter? never mind. 
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("unroll-loops")
//#pragma GCC target("sse,sse2,sse3,sse4,popcnt,abm,mmx,avx,avx2")
#include<bits/stdc++.h>
#define For(i,a,b) for(int i=(a);i<=(b);++i)
#define Rep(i,a,b) for(int i=(a);i>=(b);--i)
#define ll long long
//#define ull unsigned long long
//#define int long long
#define SZ(x) ((int)((x).size()))
#define ALL(x) (x).begin(),(x).end()
using namespace std;
inline int read()
{
	char c=getchar();int x=0;bool f=0;
	for(;!isdigit(c);c=getchar())f^=!(c^45);
	for(;isdigit(c);c=getchar())x=(x<<1)+(x<<3)+(c^48);
	return f?-x:x;
}

#define fi first
#define se second
#define pb push_back
#define mkp make_pair
typedef pair<int,int>pii;
typedef vector<int>vi;

#define maxn 500005
#define inf 0x3f3f3f3f

int n;
vi e[maxn],g1[maxn],g2[maxn];
vector<vi>out;

bool vis[maxn];

vi que;

bitset<105>bs[105],tmp;
bool add(vi p){
	tmp.set();
	int hav=0;
	For(i,0,n-1){
		tmp.reset(p[i]);
		bs[p[i]]&=tmp;
		hav|=(bs[p[i]].count()>1);
	}
	return !hav;
}

void dfs(int u,int pa){
	que.pb(u);
	for(int v:g1[u]) if(v!=pa) dfs(v,u);
	for(int v:g2[u]) if(v!=pa) dfs(v,u);
	reverse(ALL(g1[u]));
}

void my1(){
	For(i,1,n) if(e[i].size()==1){
		que.clear();
		dfs(i,0);
		reverse(ALL(que));
		out.pb(que);
	}
}

void work()
{
	n=read();
	For(i,1,n) e[i].clear(),g1[i].clear(),g2[i].clear(),vis[i]=0; out.clear();
	For(i,1,n) {
		bs[i].reset();
		For(j,1,n) bs[i][j]=1;
	}
	
	For(i,2,n){
		int u=read(),v=read();
		e[u].pb(v),e[v].pb(u);
	}
	
	For(i,1,n) if(e[i].size()==1 && !vis[i]) {
		vis[i]=1;
		int u=i,pre=0;
//		while(1){
//			int v=0;
//			for(int x:e[u]) if(x!=pre) v=x;
//			if(!v||e[v].size()>2)break;
//			vis[v]=1,pre=u,u=v;
//		}
	}
	
	For(i,1,n){
		for(int v:e[i]){
			if(vis[i]||vis[v])g1[i].pb(v);
			else g2[i].pb(v);
		}
	}
	
	bool flag=0,qaq=0;
	int cnt=0,fir=0;
	
	For(i,1,n) if(!vis[i]){
		qaq=1;
		int sum=0;
		for(int v:e[i]) sum+=(!vis[v]);
		if(sum<=1){
			++cnt; fir=i;
			que.clear();
			dfs(i,0);
			reverse(ALL(que));
			out.pb(que);
		//	for(int x:que) cout<<x<<" "; cout<<" que\n";
			if(add(que)){
				flag=1;
				break;
			}
		}
	}
	if(cnt==1) {
		que.clear();
		dfs(fir,0);
		reverse(ALL(que));
	//	for(int x:que) cout<<x<<" "; cout<<" Que\n";
		out.pb(que);
		flag|=add(que);
	}
	
	if(!qaq) my1(),flag=1;
	
//	For(i,1,n) For(j,1,n) cout<<bs[i][j]<<" \n"[j==n];
	
	assert(flag);
	
	cout<<SZ(out)<<"\n";
	for(auto it:out){
		for(int x:it)cout<<x<<" ";
		cout<<"\n";
	}
}

signed main()
{
	int T=read();
	while(T--)work();
	return 0;
}
/*

*/