/******************************************************************************
* Sample solution for the Tour problem in NWERC'03
* Author: Andreas Björklund
******************************************************************************/
#include <stdio.h>

#define MAX_JUNCTIONS (200)
#define MAX_STREETS (1000)

int jstreets[MAX_JUNCTIONS][MAX_JUNCTIONS];
int jnbr[MAX_JUNCTIONS];
int streets[MAX_STREETS][2];
int cap[MAX_JUNCTIONS];
int par[MAX_JUNCTIONS];
int path[MAX_JUNCTIONS];
int vis[MAX_JUNCTIONS];
int nstr;

int augment(int who, int cnt)
{
  if (cap[who]<0)
  {
    return cnt;
  }
  else
  {
    if (!vis[who])
    {
      int i,ans;
      ans = 0;
      vis[who] = 1;
      for (i=0;i<jnbr[who] && !ans;i++)
      {
        int sel = jstreets[who][i];
        if (streets[sel][0] == who)
        {
          path[cnt] = sel;
          ans = augment(streets[sel][1],cnt+1);
        }
      }
      return ans;
    }
    else
      return 0; 
  }  
}

int main(void)
{
  int i,j,k,T,n,m,augpath;
  scanf("%d",&T);
  for (i=0;i<T;i++)
  {
    scanf("%d %d",&n,&m);
    for (j=0;j<n;j++)
    {
      par[j]=0;
      cap[j]=0;
      jnbr[j]=0;
    }
    nstr=0; 
    for (j=0;j<m;j++)
    {
      int x,y,one;
      scanf("%d %d %d",&x,&y,&one);  
      x--;y--;
      if (!one && x!=y)
      {
        // Only remember streets which are bidirectional
        // but impose a direction for now on these...
        streets[nstr][0]=x;
        streets[nstr][1]=y;
        jstreets[x][jnbr[x]++] = nstr; // Add streets to junction-to-street mapping
        jstreets[y][jnbr[y]++] = nstr;
        nstr++;
      }
      cap[x]++; // update capacity of the read street
      cap[y]--;
      par[x]++; // The number of streets of every junction must be even
      par[y]++;
    }
    
    // Solve    
    augpath=1;
    for (j=0;j<n && augpath;j++) // Check if some junction have odd degree => no tour.
      if (par[j] & 1) augpath=0;
      
    for (j=0;j<n && augpath;j++)
    {
      // Find junction with positive capacity and try to decrease it by two
      // while only affecting another junctions (negative) capacity by an increase by two
      while (cap[j]>0 && augpath)
      {
        int q,plen;
        for (q=0;q<n;q++) vis[q]=0;
        if (plen=augment(j,0))
        {
          // update flow (reverse streets and change cap of origin and terminus junction)
          for (k=0;k<plen;k++)
          {
            int tmp;
            tmp=streets[path[k]][0];
            streets[path[k]][0]=streets[path[k]][1];
            streets[path[k]][1]=tmp;
          }
          cap[j]-=2;
          cap[streets[path[plen-1]][0]]+=2;
        }
        else
        {
          augpath=0;
        }
      }
    }
    if (augpath)
      printf("possible\n");
    else
      printf("impossible\n");     
  }
  return 0;
}