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

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