#include <bits/stdc++.h>
using namespace std;
const int maxn = 2020;
struct Edge { int v, w; };
vector<Edge> g[maxn];
int T, n, m;

// SPFA
int dis[maxn], cnt[maxn];
bool ins[maxn]; // 判断是否在队列中
bool spfa() {
    stack<int> stk;
    memset(dis, 0x3f, sizeof(int)*(n+1));
    memset(cnt, 0, sizeof(int)*(n+1));
	memset(ins, 0, sizeof(bool)*(n+1));
    dis[1] = 0;
    stk.push(1);
    while (!stk.empty()) {
        int u = stk.top();
        stk.pop();
        ins[u] = false;
        if (++cnt[u] > n * 10) 
        	return true;
        for (auto e : g[u]) {
            int v = e.v, w = e.w;
            if (dis[v] > dis[u] + w) {
                dis[v] = dis[u] + w;
                if (!ins[v])
                    ins[v] = true, stk.push(v);
            }
        }
    }
    return false;
}

int main() {
	scanf("%d", &T);
	while (T--) {
		scanf("%d%d", &n, &m);
		for (int i = 1; i <= n; i++)
			g[i].clear();
	    for (int i = 0; i < m; i++) {
	        int u, v, w;
	        scanf("%d%d%d", &u, &v, &w);
	        g[u].push_back({v, w});
	        if (w >= 0)
	        	g[v].push_back({u, w});
	    }
	    puts(spfa() ? "YES" : "NO");
	}
    return 0;
}