H

#include <bits/stdc++.h>

using namespace std;

#define ll     long long
#define _test   int _TEST; cin>>_TEST; while(_TEST--)

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);

    _test
    {
        ll int n, m;
        cin>>n>>m;

        vector<vector<pair<ll int, ll int>>> graph(n+1);

        for(int i=0; i<m; i++)
        {
            ll int a, b, d;
            cin>>a>>b>>d;

            graph[a].push_back({b, -d});
            graph[b].push_back({a, d});
        }

        map<ll int, set<int>> mp;
        ll int f = 1;
        vector<ll int> vis(n+1);

        function <void(ll int, ll int)> DFS = [&](ll int u, ll int dist)
        {
            mp[dist].insert(u);

            vis[u] = 1;

            for(auto [v, d]: graph[u])
            {
                if(!vis[v])
                    DFS(v, dist+d);
                else
                    f &= (mp[dist+d].find(v) != mp[dist+d].end());
            }
        };

        for(int i=1; i<=n && f; i++)
        {
            if(vis[i])      continue;

            mp.clear();
            DFS(i, 0);
        }

        if(f)       cout<<"YES\n";
        else        cout<<"NO\n";
    }
}