#include <bits/stdc++.h>
using namespace std;
namespace Slongod{
constexpr int N = 2e5+7 , inf = 0x3f3f3f3f;
int n , m , root , ans , add_flag , lefn[N] , dfn[N] , rdfn[N]; vector <int> g[N] , lef;
void dfs(int u , int fa)
{
    dfn[u] = int(lef.size());
    if (g[u].size() == 1){lef.push_back(u);}
    for (auto v : g[u]) {
        if (v != fa) {
            dfs(v , u);
        }
    } rdfn[u] = int(lef.size());
}
void main()
{
    auto clear = [&]() {
        for (int i = 1; i <= n + 1; i++) {
            vector<int>().swap(g[i]); lefn[i] = 0;
        } m = 0; root = 0; lef.clear(); add_flag = 0; ans = 0;
    };
    int T; cin >> T;
    while(T--) {
        cin >> n; clear();
        for (int i = 1 , u , v; i < n; i++){cin >> u >> v; g[u].push_back(v); g[v].push_back(u);}
        for (int i = 1; i <= n; i++){m += (g[i].size() == 1); root = (g[i].size() > 2 ? i : root);}
        if (m == 2) {
            for (int i = 1; i <= n; i++){if (g[i].size() == 1){cout << i << ' ';}} cout << '\n';
            for (int i = 1; i <= n; i++){if (g[i].size() == 1){cout << i << ' ';}} cout << '\n';
            cout << '\n'; continue;
        } else if (m % 2 == 0){
            n++; g[n].push_back(root); g[root].push_back(n); add_flag = 1;
        } dfs(root , root); m = int(lef.size());
        for (int i = 1; i <= n; i++) {
            if (g[i].size() > 2) {
                if (!((rdfn[i] - dfn[i]) & 1)) {
                    lefn[(rdfn[i]+dfn[i]) / 2 - 1]++;
                } else if (rdfn[i] - dfn[i] != m) {
                    lefn[((dfn[i]+m+rdfn[i]) / 2 - 1) % m]++;
                }
            }
        } lefn[0] = inf;
        for (int i = 0; i < m; i++) {
            if (lefn[i] < lefn[ans]) {
                ans = i;
            }
        } assert(!lefn[ans]);
        auto print = [&](int x , int y) {
            x = (x + m) % m; y = (y + m) % m;
            if (x == y){y = (y + 1) % m;}
            x = lef[x]; y = lef[y];
            if (x == n and add_flag){x = root;}
            if (y == n and add_flag){y = root;}
            cout << x << ' ' << y << '\n';
        };
        for (int i = 0; i < m / 2 + 1; i++) {
            print(ans - i , ans + i + 1);
        } cout << '\n';
    }
}
}int main()
{
    #ifndef ONLINE_JUDGE
    freopen("in.in" , "r" , stdin);
    #endif
    ios :: sync_with_stdio(0);
    cin.tie(0) , cout.tie(0);
    return Slongod :: main(),0;
}