// P3385：检测从 1 可达的负环。C++11。
#include <iostream>
#include <vector>
#include <queue>
using namespace std;
using ll = long long;
struct Edge { int v, w; };

bool hasNegativeCycle(const vector<vector<Edge>>& g) {
    int n = static_cast<int>(g.size()) - 1;
    const ll INF = (1LL << 60);
    vector<ll> dis(n + 1, INF);
    vector<int> len(n + 1, 0);
    vector<bool> inq(n + 1, false);
    queue<int> q;
    dis[1] = 0;
    q.push(1); inq[1] = true;
    while (!q.empty()) {
        int u = q.front(); q.pop();
        inq[u] = false;
        for (auto e : g[u]) {
            int v = e.v;
            ll nd = dis[u] + e.w;
            if (nd >= dis[v]) continue;
            dis[v] = nd;
            len[v] = len[u] + 1;
            if (len[v] >= n) return true;
            if (!inq[v]) {
                q.push(v);
                inq[v] = 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<vector<Edge>> g(n + 1);
        for (int i = 0; i < m; ++i) {
            int u, v, w; cin >> u >> v >> w;
            g[u].push_back({v, w});
            if (w >= 0) g[v].push_back({u, w});
        }
        bool bad = hasNegativeCycle(g);
        cout << (bad ? "YES" : "NO") << '\n';
    }
}