#include <bits/stdc++.h>
using namespace std;
const int sz = 2020202;
#define next next_
int node[sz], next[sz], to[sz], w[sz], e;
void ins(int x, int y, int v)
{e++; next[e] = node[x]; node[x] = e; to[e] = y; w[e] = v;}
int N, Q, ans;

int vis[sz], parity[sz];
void dfs(int x) {
  vis[x] = 1;
  for (int j = node[x]; j; j = next[j])
    if (!vis[to[j]]) {
      parity[to[j]] = parity[x] ^ w[j];
      dfs(to[j]);
    } else if (parity[to[j]] ^ parity[x] ^ w[j]) ans = 0;
}

void clr() {
  for (int i = 1; i <= N; i++) node[i] = vis[i] = parity[i] = 0;
  for (int i = 1; i <= e; i++) next[i] = to[i] = w[i] = 0;
  e = 0; ans = 1;
}
void doit() {
  int i, j, v;
  clr();
  scanf("%d %d", &N, &Q);
  while (Q--) {
    scanf("%d %d %d", &i, &j, &v);
    ins(i, j, v); ins(j, i, v);
  }
  for (i = 1; i <= N; i++) if (!vis[i]) dfs(i);
  printf(ans ? "yes\n" : "no\n");
}

int main() {int T; scanf("%d", &T); while (T--) doit(); return 0;}