#include <bits/stdc++.h>
#define IOS ios::sync_with_stdio(0) , cin.tie(0) , cout.tie(0)
#define INF 1e12
#define int long long
using namespace std;

const int N = 3e3 + 10, M = 6e3 + 10;
int T , n , m , cnt[N] , head[N] , l , dist[N];
bool flag[N]; 
struct e{
	int u , v , w , nxt;
} fs[M];

void add(int u , int v , int w) {
	fs[++ l] = {u , v , w , head[u]};
	head[u] = l;
}

bool spfa(int s) {
	queue <int> q;
	dist[s] = 0;
	flag[s] = 1;
	q.push(s);
	cnt[s] ++;
	while(!q.empty()) {
		int t = q.front();
		q.pop();
		flag[t] = 0;
		for(int i = head[t]; i ;i = fs[i].nxt){
			int j = fs[i].v;
			int cost = fs[i].w;
			if(dist[j] > dist[t] + cost) {
				dist[j] = dist[t] + cost;
				if(!flag[j]) {
					flag[j] = 1;
					cnt[j] ++;
					if(cnt[j] >= n) return 1;
					q.push(j);
				}
			}
		}
	}
	return 0;
}

signed main() {
    IOS;
    for(cin >> T; T ;-- T) {
    	l = 0;
    	for(int i = 1;i <= n;++ i) {
			head[i] = 0;
			cnt[i] = 0;
			flag[i] = 0;
			dist[i] = INF; 
		} 
    	cin >> n >> m;
    	for(int i = 1;i <= m;++ i){
    		int u , v , w;
    		cin >> u >> v >> w;
			if(w >= 0) {
				add(u , v , w);
				add(v , u , w);
			}
			else add(u , v , w);
		}
		if(spfa(1)) cout << "YES\n";
		else cout << "NO\n";
	}
    return 0;
}