#include<bits/stdc++.h>
using namespace std;
typedef long long ll;

constexpr ll INF = 2147483647;
constexpr int N = 1e5+1;

int n,m;

struct Node {
	int v;
	ll w;
};
vector<Node> e[N];
bitset<N> inq;
ll dis[N],val;
ll neg[N];
bool f = 0;

void spfa(int s) {
	for(int i=1; i<=n; ++i) dis[i] = INF,inq[i] = 0,neg[i] = 0;
	deque<int> q;
	q.push_back(s);
	inq[s] = 1;
	neg[s] = 1;
	dis[s] = 0;
	while(!q.empty()) {
		int u = q.front();
		q.pop_front();
		inq[u] = 0;
		++neg[u];
		if(neg[u] >= n) {
			f = 1;
			break;
		}
		for(const auto &x:e[u]) {
			auto v = x;
			if(dis[v.v] > dis[u] + v.w) {
				dis[v.v] = dis[u] + v.w;
				if(!inq[v.v]) {
					inq[v.v] = 1;
					if(!q.empty()&&dis[v.v] > dis[q.front()]) {
						q.push_back(v.v);
					} else q.push_front(v.v);
					if(dis[q.front()] > dis[q.back()]) swap(q.front(),q.back());
				}
			}
		}
	}
	if(f){
		cout << "YES" << '\n';
	}else cout << "NO" << '\n';
}

int main() {
	ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
	int T;
	cin >> T;
	while(T --) {
		f = 0;
		cin >> n >> m ;
		for(int i=1;i<=n;++i) e[i].clear();
		for(int i=1; i<=m; ++i) {
			int x,y,w;
			cin >> x >> y >> w;
			if(w < 0){
				e[x].push_back({y,w});
			}else{
				e[x].push_back({y,w});
				e[y].push_back({x,w});
			}
		}
		spfa(1);
	}

	return 0;
}

没看懂有什么问题