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#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<stdlib.h>
#include<iostream>
#include<map>
#include<set>
using namespace std;
typedef pair<int,int> P;
set<P> sk;
int main()
{
    int T;
    cin>>T;
    while(T--)
    {
        sk.clear();
        int n,m;
        cin>>n>>m;
        for(int i=0;i<m;i++)
        {
            int u,v;
            cin>>u>>v;
            sk.insert(P(u,v));
            sk.insert(P(v,u));
        }
        printf((int)sk.size()==2*n-2?"YES\n":"NO\n");
    }
    return 0;
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