#include <bits/stdc++.h>
using std::bitset;
using std::cout;
using std::deque;
using std::endl;
using std::greater;
using std::lower_bound;
using std::make_pair;
using std::map;
using std::max;
using std::min;
using std::multimap;
using std::multiset;
using std::nth_element;
using std::pair;
using std::priority_queue;
using std::queue;
using std::reverse; 
using std::set;
using std::sort;
using std::sqrt;
using std::stable_sort;
using std::string;
using std::swap;
using std::unique;
using std::upper_bound;
using std::vector;
typedef long long li;
typedef long double lf; 

inline long long read(){
	long long ans = 0, f = 1;
	char ch = getchar();
	while(ch < '0' || ch > '9'){
		f = (ch == '-') ? -1 : 1;
		ch = getchar();
	}
	while(ch <= '9' && ch >= '0'){
		ans = ans * 10 + (ch ^ 48);
		ch = getchar();
	}
	return ans * f;
} 

li n, m;
li degree[110], val[110];
vector<li> a[110], ans[110];

void dfs(li u, li fa){
    // cout << "u = " << u << endl;
    ans[m].push_back(u);
    vector<li> temp;
    for(li v : a[u]){
        if(v != fa && a[v].size() == 1) temp.push_back(v);
    }
    if(val[u] && temp.size()){
        reverse(temp.begin(), temp.end());
        val[u] ^= 1;
    }
    for(li v : temp) ans[m].push_back(v);
    for(li v : a[u]){
        if(v != fa && a[v].size() > 1) dfs(v, u);
    }
}

int main(){
    // freopen("wonderful.ans", "r", stdin);
    // freopen("www.ww", "w", stdout);
	li T = read();
    while(T--){
        m = 0, n = read();
        memset(degree, 0, sizeof degree);
        for(li i = 1; i <= n; i++) a[i].clear(), ans[i].clear();
        for(li i = 1; i < n; i++){
            li u = read(), v = read();
            degree[u]++, degree[v]++;
            a[u].push_back(v), a[v].push_back(u);
        }
        memset(degree, 0, sizeof degree);
        for(li i = 1; i <= n; i++){
            if(a[i].size() != 1){
                for(li j : a[i]){
                    degree[i] += (a[j].size() >= 2);
                }
                // cout << i << " " << degree[i] << endl;
                if(degree[i] == 1){
                    m++;
                    dfs(i, 0);
                    reverse(ans[i].begin(), ans[i].end());
                }
            }
        }
        printf("%lld\n", m);
        for(li i = 1; i <= m; i++){
            for(li v : ans[i]) printf("%lld ", v);
            printf("\n");
        }
    }
    return 0;
}