#include<iostream>
#include<cstdio>
#include<cstring>
#include<queue>
#define inf  0x3f3f3f3f
using namespace std;
long long d[20001];
long long v[20001],tag[20001];
long long n,m,tot,sum;
struct note{
	long long next,to,cost;
}edge[100000];
long long head[100000];
queue<long long>q;
void insert(long long x,long long y,long long z)
{
	edge[++tot].to=y;
	edge[tot].cost=z;
	edge[tot].next=head[x];
	head[x]=tot;
}
bool spfa()
{
//	for(long long i=1;i<=n;i++)d[i]=inf;
//	for(long long i=1;i<=n;i++)tag[i]=0; 
	d[1]=0;
	 v[1]=1;
	 q.push(1);
	 tag[1]=0;
	// sum=1;
	 while(q.size())
	 {
	 	long long t=q.front();
	 	q.pop();
	 	v[t]=0;
	 	for(long long i=head[t];i;i=edge[i].next)
	 	{
	 	//			cout<<t<<" "<<edge[i].to<<" "<<tag[t]<<" "<<tag[edge[i].to]<<" "<<d[t]<<" "<<d[edge[i].to]<<" "<<edge[i].cost<<endl;
	 		if(d[t]+edge[i].cost<d[edge[i].to])
	 		{
	 			d[edge[i].to]=d[t]+edge[i].cost;
	 				tag[edge[i].to]=tag[t]+1;
	 		//			cout<<t<<" "<<edge[i].to<<" "<<tag[t]<<" "<<tag[edge[i].to]<<" "<<d[t]<<" "<<d[edge[i].to]<<endl;
	 	//				cout<<endl;
	 				if(tag[edge[i].to]>=n)return true;
	 			if(!v[edge[i].to])
	 			{
	 //				++tag[edge[i].to];
	 				//++sum;
	 //				if(sum>=tot*n)return false;
	 			//	else if(tag[edge[i].to]>=n)return false;
	 			q.push(edge[i].to);
	 			v[edge[i].to]=1;
				 }
			 }
		 }
	 }
	 return false;
}
void Init()
{
	for(int i=0;i<100000;i++)edge[i].next=0;
	for(int i=0;i<100000;i++)head[i]=0;
	for(int i=1;i<=n;i++)d[i]=inf;
	memset(v,0,sizeof(v));
	memset(tag,0,sizeof(tag));
		tot=0;
}
int main()
{
	long long T;
	scanf("%lld",&T);
	while(T--)
	{
		scanf("%lld%lld",&n,&m);
	//	memset(edge,0,sizeof(edge));
	//	memset(v,0,sizeof(v));
	Init();
	while(!q.empty())q.pop();
		for(long long i=1;i<=m;i++)
		{
			long long v,u,w;
			scanf("%lld%lld%lld",&v,&u,&w);
			if(w>=0)
			{
				insert(u,v,w);
				insert(v,u,w);
			}
			else insert(u,v,w);
		}
		if(spfa())cout<<"YES"<<endl;
		else cout<<"NO"<<endl;
	}
 }