#include<bits/stdc++.h>

using namespace std;

#define N 10005

int t,n,m,color[N];

vector<int> adj[N];

bool c;

void dfs(int p){

    for(auto e:adj[p]){

        if(color[e]==0){

            if(color[p]==1) color[e]=2;

            else color[e]=1;

            dfs(e);

        }else if(color[e]==color[p]){

            c=1;

            return;

        }

    }

}

signed main(){

    ios::sync_with_stdio(0);

    cin.tie(0);

    cin>>t;

    while(t--){

        cin>>n>>m;

        c=0;

        memset(color,0,sizeof(color));

        for(int i=0,u,v;i<m;i++){

            cin>>u>>v;

            adj[u].push_back(v);

            adj[v].push_back(u);

        }

        int i;

        for(i=0;i<n;i++){

            if(color[i]==0)

                dfs(i);

            if(c) break;

        }

        if(c) cout<<"no\n";

        else cout<<"yes\n";

        for(i=0;i<n;i++) adj[i].clear();

    }

}