// 教学版 Bellman-Ford 判环；输入格式与 P3385 一致。C++11。
#include <iostream>
#include <vector>
using namespace std;
using ll = long long;
struct Edge { int u, v, w; };

bool hasNegativeCycle(int n, const vector<Edge>& edges, int s) {
    const ll INF = (1LL << 60);
    vector<ll> dis(n + 1, INF);
    dis[s] = 0;
    for (int k = 1; k <= n; ++k) {
        auto old = dis;
        bool changed = false;
        for (auto e : edges) {
            if (old[e.u] == INF) continue;
            ll nd = old[e.u] + e.w;
            if (nd < dis[e.v]) {
                dis[e.v] = nd;
                changed = true;
            }
        }
        if (!changed) return false;
        if (k == n) return true;
    }
    return false;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int T;
    if (!(cin >> T)) return 0;
    while (T--) {
        int n, m; cin >> n >> m;
        vector<Edge> edges;
        for (int i = 0; i < m; ++i) {
            int u, v, w; cin >> u >> v >> w;
            edges.push_back({u, v, w});
            if (w >= 0) edges.push_back({v, u, w});
        }
        cout << (hasNegativeCycle(n, edges, 1) ? "YES" : "NO") << '\n';
    }
}