#include <queue>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
const int N = 1e5 + 10;
int h[N], w[N], e[N], ne[N], idx;
int dist[N], cnt[N];
bool st[N];
int n, m;
void add(int a, int b, int c)
{
    e[idx] = b;
    w[idx] = c;
    ne[idx] = h[a];
    h[a] = idx++;
}
bool spfa()
{
    queue<int> q;
    q.push(1);
    st[1] = true;
    while(q.size())
    {
        auto t = q.front();
        q.pop();
        st[t] = false;
        for (int i = h[t]; i != -1; i = ne[i])
        {
            int j = e[i];
            if(dist[j] > dist[t] + w[i])
            {
                dist[j] = dist[t] + w[i];
                cnt[j] = cnt[t] + 1;
                if(cnt[j] >= n)
                    return true;
                if(!st[j])
                {
                    q.push(j);
                    st[j] = true;
                }
            }
        }
    }
    return false;
}
int main ()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int T;
    cin >> T;
    while(T --)
    {
        memset(h, -1, sizeof h);
        memset(dist, 0, sizeof dist);
        memset(st, false, sizeof st);
        cin >> n >> m;
        for (int i = 1; i <= m; i ++)
        {
            int a, b, c;
            cin >> a >> b >> c;
            add(a, b, c);
        }
        if(spfa())
            cout << "YES" << endl;
        else
            cout << "NO" << endl;
    }
    return 0;
}