#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 5e3 + 10;
const int MOD = 1000000007;
const int INF = 1e9+10;
int n,m,s,cnt = 0;
int to[N],nxt[N],val[N],head[N];
void biuld_edge(int x,int y,int w)
{
	nxt[++cnt] = head[x];
	head[x] = cnt;
	val[cnt] = w;
	to[cnt] = y;
	if(w>=0){
		nxt[++cnt] = head[y];
		head[y] = cnt;
		val[cnt] = w;
		to[cnt] = x;
	}
}
int dis[N];
int vis[N];
bool op[N];
bool SPFA(){
	for (int i = 1; i <=n; i++)
	{
		dis[i] = INF;
		vis[i] = 0;
		op[i] = false;
	}
	dis[1] = 0;
	vis[1] = 1;
	queue<int> ty;
	ty.push(1);
	while(!ty.empty()){
		int x = ty.front();
		op[x] = false;
		ty.pop();
		for (int i = head[x]; i!=-1; i = nxt[i])
		{
			if(dis[x]+val[i]<dis[to[i]]){
				dis[to[i]] = dis[x] + val[i];
				if(!op[to[i]]){
					ty.push(to[i]);
					op[to[i]] = true;
					vis[to[i]]++;
					if(vis[to[i]]>=n) return false;
				}
			}
		}
	}
	return true;
}
void solve() {
	memset(head,-1,sizeof(head));
	cin>>n>>m;
	for (int i = 1; i <=m; i++)
	{
		int x,y,w;
		cin>>x>>y>>w;
		biuld_edge(x,y,w);
	}
	if(SPFA()) cout<<"NO"<<endl;
	else cout<<"YES"<<endl;
	return;
}

int main() {
	std::ios_base::sync_with_stdio(false);
	std::cin.tie(nullptr);
	std::cout.tie(nullptr);
	int T;
	T = 1;
	cin >> T;
	while (T--) {
		solve();
	}
	return 0;
}

开5e3 有几个点tle了开成5e4就过了？