#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const ll N = 1e4 + 5, M = 5e5 + 5, inf = (1 << 31) - 1;
ll n, m, s, ans[N], t;
struct node
{
	ll x, y, k;
	void clear()
	{
		x = y = k = 0;
		return;
	}
	void read()
	{
		cin >> x >> y >> k;
		return;
	}
} e[M];
void SPFA()
{
	for (int i = 1; i < M; i++)
		e[i].clear();
	cin >> n >> m;
	ll p = m;
	for (int i = 1; i <= m; i++)
	{
		e[i].read();
		if (e[i].k >= 0)
			e[++p] = {e[i].y, e[i].x, e[i].k};
	}
	for (int i = 1; i <= n; i++)
		ans[i] = inf;
	ans[1] = 0;
	for (int i = 1; ; i++)
	{
		bool flag = false;
		for (int j = 1; j <= m; j++)
			if (ans[e[j].y] > ans[e[j].x] + e[j].k)
			{
				ans[e[j].y] = ans[e[j].x] + e[j].k;
				flag = true;
			}
		if (!flag and i <= n)
			break;
		if (flag and i > n)
		{
			cout << "NO\n";
			return;
		}
	}
	cout << "YES\n";
	return;
}
int main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	cin >> t;
	while (t--)
		SPFA();
	return 0;
}

qwq