#include<bits/stdc++.h>
using namespace std;
#define int long long
const int N=3e3+5;
struct edge{int v,w;};
vector<edge> e[N];
int dis[N],cnt[N];
bool vis[N];
int n,m;
queue<int> q;
bool spfa(int s){
	memset(vis,0,sizeof(vis));
	memset(cnt,0,sizeof(cnt));
	for(int i=1;i<=n;i++)dis[i]=0x3f3f3f3f;
	dis[s]=0;vis[s]=1;
	q.push(s);
	while(!q.empty()){
		int u=q.front();q.pop();vis[u]=0;
		for(auto ed: e[u]){
			int v=ed.v, w=ed.w;
			if(dis[v]>dis[u]+w){
				dis[v]=dis[u]+w;
				cnt[v]=cnt[u]+1;
				if(cnt[v]>=n)return 1; //存在负环
				if(!vis[v])q.push(v),vis[v]=1;
			}
		}
	}
	return 0;
}
signed main(){
	ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
	int t;cin>>t;
	while(t--){
		cin>>n>>m;
		for(int i=1;i<=n;i++)e[i].clear();
		
		for(int i=1;i<=m;i++){
			int a,b,c;cin>>a>>b>>c;
			if(c>=0){
				e[a].push_back({b,c});
				e[b].push_back({a,c});
			}
			else e[a].push_back({b,c});
		}
		cout<<(spfa(1)?"YES\n":"NO\n");
	}
	return 0;
}