#include<bits/stdc++.h>
using namespace std;

typedef long long ll;
const int N=103;
int n,m,tim=0,fa[N],sz[N],leaf[N],a[N][N];
bool ban[N],nb[N];
vector<int>ve[N];
void Dfs(int x){for(int y:ve[x])if(y!=fa[x])fa[y]=x,Dfs(y);}
bool Cmp(int x,int y)
{
	bool fx=ve[x].size()==1,fy=ve[y].size()==1;
	return fx!=fy?fx>fy:nb[x]<nb[y];
}
void Ans(int x,int Fa)
{
	a[m][++tim]=x;sort(ve[x].begin(),ve[x].end(),Cmp);
	for(int y:ve[x])if(y!=Fa)Ans(y,x);
}
void Solve()
{
	cin>>n;m=0;
	for(int i=1;i<=n;i++)ve[i].clear(),sz[i]=leaf[i]=ban[i]=nb[i]=0;
	for(int i=1,x,y;i<n;i++)cin>>x>>y,ve[x].push_back(y),ve[y].push_back(x);
	Dfs(1);
	for(int x=1;x<=n;x++)if(ve[x].size()==1)for(int y:ve[x])leaf[y]++;
	for(int x=1;x<=n;x++)if(ve[x].size()==1&&!ban[x])
	{
		nb[x]=1;
		for(int y:ve[x])
		{
			sz[y]++;m++;tim=0;a[m][++tim]=x;Ans(y,x);
			for(int z:ve[x])if(z!=y)Ans(z,x);
		}
		for(int y:ve[x])if(sz[y]+1==leaf[y])for(int z:ve[y])if(ve[z].size()==1)ban[z]=1;
	}
	cout<<m<<endl;
	for(int t=1;t<=m;t++,cout<<endl)for(int i=n;i;i--)cout<<a[t][i]<<" ";
}
int main()
{
	ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
	int T;cin>>T;
	while(T--)Solve();
	return 0;
}