//网络流判定混合图欧拉回路

//通过网络流使得各点的出入度相同则possible，否则impossible

//残留网络的权值为可改变方向的次数，即n个双向边则有n次

//Time:157Ms    Memory:348K

#include <iostream>

#include<cstring>

#include<cstdio>

#include<algorithm>

#include<queue>

using namespace std;

#define MAXN 205

#define INF 0x3f3f3f3f

int n,m;

int s,t;

int dif[MAXN];

int res[MAXN][MAXN];    //残留网络-代表可变方向数

int pre[MAXN];

bool bfs()

{

    memset(pre,-1,sizeof(pre));

    queue<int> q;

    q.push(s); pre[s] = 0;

    while(!q.empty()){

        int cur = q.front();

        q.pop();

        for(int i = 1; i <= t; i++)

        {

            if(pre[i] == -1 && res[cur][i])

            {

                pre[i] = cur;

                if(i == t) return true;

                q.push(i);

            }

        }

    }

    return false;

}

int EK()

{

    int maxFlow = 0;

    while(bfs()){

        int mind = INF;

        for(int i = t; i != s; i = pre[i])

            mind = min(mind, res[pre[i]][i]);

        for(int i = t; i != s; i = pre[i])

        {

            res[pre[i]][i] -= mind;

            res[i][pre[i]] += mind;

        }

        maxFlow += mind;

    }

    return maxFlow;

}

int main()

{

    //freopen("in.txt", "r", stdin);

    int T;

    scanf("%d", &T);

    while(T--){

        memset(dif,0,sizeof(dif));

        memset(res,0,sizeof(res));

        scanf("%d%d", &n, &m);

        int total = 0;

        s = 0; t = n+1;

        for(int i = 0; i < m; i++)

        {

            int u,v,t;

            scanf("%d%d%d", &u,&v,&t);

            dif[u]++;   dif[v]--;

            if(t == 0) res[u][v] += 1;  //重边则可变方向+1

        }

        bool flag = true;

        for(int i = 1; i <= n; i++)

        {

            if(dif[i] > 0) {    //出度多-通过源点给予奇数入度

                res[s][i] = dif[i]/2;

                total += dif[i]/2;

            }

            if(dif[i] < 0) res[i][t] = -dif[i]/2;  //入度多-通过汇点给予奇数出度

            if(abs(dif[i]) % 2 == 1)

            {

                flag = false;

                break;

            }

        }

        (flag && EK() == total)? printf("possible\n"): printf("impossible\n");

    }

    return 0;

}