#include <algorithm>
#include <cstring>
#include <cstdio>
#include <vector>
#include <queue>
using namespace std;
class edge{
	public:
		edge(int x, int y, int z, int zz){v = x, w = y, c = z, nxt = zz;}
		int v, w, c, nxt;
};
class graph{
	private:
		vector<int> head;vector<edge> e;
	public:
		void init(int n){head.clear(), e.clear();for (int i = 0;i <= n;i ++) head.emplace_back(-1);}
		graph(){}graph(int n){init(n);}
		inline int addedge(int u, int v, int w = 0, int c = 0){e.emplace_back(v, w, c, head[u]), head[u] = e.size() - 1;return e.size() - 1;}
		inline int add2edge(int u, int v, int w = 0){int tmp = addedge(u, v, w);addedge(v, u, w);return tmp;}
		inline int addfedge(int u, int v, int w, int c = 0){int tmp = addedge(u, v, w, c);addedge(v, u, 0, -c);return tmp;}
		inline int& h(int u){return head[u];}
		inline edge& operator[](int i){return e[i];}
}G;
const int N = 200005;vector<int> to[N], ed[N];
int t, n, m, a[N], d[N], L[N], R[N], rt, p;
void su2(int u, int fa, int tp){
	if (d[u] != 2){if (tp) to[tp].push_back(u);tp = u;}
	for (int i = G.h(u);i != -1;i = G[i].nxt){
		int v = G[i].v;if (v != fa) su2(v, u, tp);
	}
}
void dfs1(int u){L[u] = m + 1;
	if (d[u] == 1) a[++ m] = u;
	for (int v : to[u]) dfs1(v);R[u] = m;
}
void dfs2(int u){int mid = L[u] + R[u] >> 1;if (u != rt){
	if (m & 1) ed[R[u] - L[u] & 1 ? mid : (mid + m / 2 - 1) % m + 1].push_back(u);
	else if (R[u] - L[u] & 1) ed[mid].push_back(u), ed[(mid + m / 2 - 1) % m + 1].push_back(u);}
	for (int v : to[u]) dfs2(v);
}
int main(){scanf("%d", &t);
	while (t --){scanf("%d", &n), G.init(n), rt = p = 1, m = 0;
		for (int i = 1;i <= n;i ++) to[i].clear(), ed[i].clear(), d[i] = 0;
		for (int i = 1, u, v;i < n;i ++)
		scanf("%d%d", &u, &v), G.add2edge(u, v), d[u] ++, d[v] ++;
		while (rt <= n && d[rt] < 3) rt ++;
		if (rt > n){int x = 0, y = 0;
			for (int i = 1;i <= n;i ++)
			if (d[i] == 1) (x ? y : x) = i;
			printf("%d %d\n%d %d\n", x, y, x, y);continue;
		}su2(rt, 0, 0), dfs1(rt), dfs2(rt);
		while (ed[p].size() > 1) p ++;
		if (ed[p].empty()){
			for (int l = p, r = p + 1, c = m / 2;c --;){
				l = l ? l : m, r = r <= m ? r : 1;
				printf("%d %d\n", a[l], a[r]), l --, r ++;
			}printf("1 2\n");continue;
		}bool flg = 0;
		int ls = L[ed[p][0]], rs = R[ed[p][0]];
		int u = a[L[ed[p][0]]], v = a[L[ed[p][0]] == 1 ? m : 1];
		for (int l = p + 1, r = p, c = m / 2;c --;){
			l --, r ++, l = l ? l : m, r = r <= m ? r : 1;
			if (l == rs && r == ls) printf("%d %d\n", u, v), flg = 1;
			printf("%d %d\n", a[l], a[r]);
			if (l == ls && r == rs) printf("%d %d\n", u, v), flg = 1;
		}if (!flg) printf("%d %d\n", u, v);
	}
}