Compiled

#include <bits/stdc++.h>

#define pb(x) push_back(x);
#define in(y) insert(y);
#define tt(t) while(t--)
#define itr ::iterator it;
#define ll long long
#define vi vector<int>
#define ii pair<int, int>
#define vii vector<ii>
#define si set<int>
#define msi map<string, int>
#define new cout<<endl
#define ff(n) for(int i=0;i<n;i++)
#define all(v) sort(v.begin(),v.end())

using namespace std;
int V=0,m,n;

int colorArr[1024];
bool isBP(int G[][1024], int src)
{
    for (int i = 0; i < V; ++i)
        colorArr[i] = -1;

    colorArr[src] = 1;

    queue <int> q;
    q.push(src);
    while (!q.empty())
    {
        int u = q.front();
        q.pop();
        for (int v = 0; v < V; ++v)
        {
            if (G[u][v] && colorArr[v] == -1)
            {
                // Assign alternate color to this adjacent v of u
                colorArr[v] = 1 - colorArr[u];
                q.push(v);
            }
            else if (G[u][v] && colorArr[v] == colorArr[u])
                return false;
        }
    }
    return true;
}
int mat[1024][1024];
int main(){
    int t;
    cin>>t;
    while(t--){

        cin>>n>>m;
        for(int i=0;i<V;i++)
            for(int j=0;j<V;j++)
                mat[i][j]=1;

        int fr,to;
        while(m--) {
            cin>>fr>>to;
            mat[fr-1][to-1]=0;
        }
        if(isBP(mat,0)) cout<<"Yes\n";
        else cout<<"No\n";

    }

    return 0;
}