// #define NDEBUG
#include<bits/stdc++.h>
#define For(i,j,k) for(int i=(j);i<=(k);i++)
#define ForD(i,j,k) for(int i=(j);i>=(k);i--)
#define int long long
#define endl '\n'
using namespace std;
bool Mbe;
const int N=105;
vector<int> E[N],S[N];
#define pb push_back
int tot,tim,deg[N],ans[N][N];
bool lf[N];
void dfs(int u,int fa){
    if(lf[u]==1) return;
    ans[tot][++tim]=u;
    for(int v:S[u]) ans[tot][++tim]=v;
    reverse(S[u].begin(),S[u].end());
    for(int v:E[u]) if(v!=fa) dfs(v,u);
}
void solve(){
    int n; cin>>n; tot=0;
    For(i,1,n) E[i].clear(),S[i].clear();
    For(i,1,n) lf[i]=0,deg[i]=0;
    For(i,1,n-1){
        int u,v; cin>>u>>v;
        E[u].pb(v),E[v].pb(u);
        ++deg[u],++deg[v];
    }
    For(u,1,n) if((int)E[u].size()==1){
        for(int v:E[u]) deg[v]--,S[v].pb(u);
        lf[u]=1;
    }
    For(i,1,n) if(!lf[i]&&deg[i]==1){
        ++tot; tim=0;
        dfs(i,0);
    }
    if(tot==1){
        For(i,1,n) if(!lf[i]&&deg[i]==1){
            ++tot; tim=0;
            dfs(i,0);
        }
    }
    cout<<tot<<endl;
    For(i,1,tot){
        ForD(j,n,1) cout<<ans[i][j]<<' ';
        cout<<endl;
    }
}
bool Med;
signed main(){
    fprintf(stderr,"%.3lf MB\n",(&Mbe-&Med)/1048576.0);
    // freopen("1.in","r",stdin), freopen("1.out","w",stdout);
    ios::sync_with_stdio(false); cin.tie(0),cout.tie(0);
    int _=1;
    cin>>_;
    while(_--) solve();
    cerr<<1e3*clock()/CLOCKS_PER_SEC<<" ms\n";
    return 0;
}