#include <algorithm>
#include <iostream>
#include <vector>

const int N = 5e5 + 5;

void Main(){

    std::cin.tie(0)->sync_with_stdio(0);

    int n,m;
    std::vector<int> p[N];

    std::cin >> n >> m;
    for (int i = 1;i <= m;i++){

        int u,v;

        std::cin >> u >> v;
        p[u].push_back(v);

    }
    for (int i = 1;i <= m;i++){

        std::sort(p[i].begin(),p[i].end());
        for (int j : p[i]) std::cout << j << ' ';
        std::cout << '\n';

    }

}

int main(){

    #ifndef ONLINE_JUDGE
        freopen("B3613.in","r",stdin);
    #endif

    std::cin.tie(0)->sync_with_stdio(0);

    int T;

    for (std::cin >> T;T--;Main());

    return 0;
}