//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;
}