/*

**  混合图欧拉回路

**  只记录各定点的出度与入度之差，有向边无用丢弃，将无向边定向，在网络中建立流量为1的边

**  另新建s和t。对于入 > 出的点u，连接边(u, t)、容量为x，对于出 > 入的点v，连接边(s, v)，

**  容量为x（注意对不同的点x不同）。之后，察看是否有满流的分配，如果是满流则存在，否则不存在

*/

#include <iostream>

#include <cstdio>

#include <cstring>

#include <queue>

#include <cmath>

using namespace std;

const int maxn = 300;

const int maxm = maxn*10;

struct node{

    int v,next,flow;

}edge[maxm];

int head[maxn],dis[maxn],deg[maxn];

int id,source,sink;

void add_edge(int u,int v,int flow){

    edge[id].v = v;edge[id].flow = flow;edge[id].next = head[u];head[u] = id++;

    edge[id].v = u;edge[id].flow =  0  ;edge[id].next = head[v];head[v] = id++;

}

bool spfa(){

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

    dis[source] = 0;

    queue<int>que;

    que.push(source);

    while(!que.empty()){

        int u = que.front();

        que.pop();

        for(int id = head[u]; id != -1; id = edge[id].next){

            int v = edge[id].v;

            if( edge[id].flow > 0 && dis[v] == -1){

                dis[v] = dis[u] + 1;

                que.push(v);

            }

        }

    }

    return dis[sink] != -1;

}

int dinic(int u,int flow){

    if( u == sink)return flow;

    int tmp = flow;

    for(int id = head[u]; id != -1; id = edge[id].next){

        int v = edge[id].v;

        if( edge[id].flow > 0 && dis[v] == dis[u] + 1){

            int  tt = dinic(v,min(edge[id].flow ,tmp));

            tmp -= tt;

            edge[id].flow -= tt;

            edge[id^1].flow += tt;

            if( tmp == 0)return flow;

        }

    }

    return flow - tmp;

}

int get_max(){

    int max_flow = 0;

    while( spfa())

    max_flow += dinic(source,100000);

    return max_flow;

}

int main(){

    int t,n,m;

    int u,v,d;

    scanf("%d",&t);

    while( t-- ){

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

        for(int i = 0; i <= n+1; i++)

        deg[i] = 0,head[i] = -1;

        id = source = 0;sink = n+1;

        while( m-- ){

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

            if( u == v)continue;

            deg[u]++,deg[v]--;

            if( d == 0)add_edge(u,v,1);

        }

        bool flg = false;

        int ans = 0;

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

            if( deg[i]%2 ){flg = true;break;}

            deg[i] /= 2;

            if( deg[i] > 0){

                ans += deg[i];

                add_edge(source,i,deg[i]);

            }

            else

            add_edge(i,sink,-deg[i]);

        }

        if( flg || ans != get_max())puts("impossible");

        else puts("possible");

    }

    return 0;

}