#include<bits/stdc++.h>
using namespace std;
const int N=2e5+10;
int id[N];
int h[N],ne[N],w[N],e[N],idx;
stack<int> q;
int scnt;
int cnt[N];
int times;
int n,m;
int dfn[N],low[N];
int ins[N];
int in[N];
vector<int> g[N];
void add(int a,int b){
    e[idx]=b,ne[idx]=h[a],h[a]=idx++;
}
void tarjan(int u){
    int i;
    dfn[u]=low[u]=times++;
    q.push(u),ins[u]=1;
    for(i=h[u];i!=-1;i=ne[i]){
        int j=e[i];
        if(!dfn[j]){
            tarjan(j);
            low[u]=min(low[u],low[j]);
        }
        else if(ins[j])
            low[u]=min(low[u],dfn[j]);
    }
    if(low[u]==dfn[u]){
        scnt++;
        while(1){
            int t=q.top();q.pop();
            ins[t]=0;
            id[t]=scnt;
            if(t==u)
            break;
        }
    }
}
bool topo(){
    int i;
    queue<int> qi;
    for(i=1;i<=scnt;i++){
        if(!in[i])
        qi.push(i);
    }
    while(qi.size()){
        if(qi.size()>1)
        return 0;
        int t=qi.front();
        qi.pop();
        for(i=0;i<g[t].size();i++){
            int k=g[t][i];
            in[k]--;
            if(!in[k])
            qi.push(k);
        }
    }
    return true;
}
int main(){
    int t;
    cin>>t;
    while(t--){
        cin>>n>>m;
        int i;
        memset(h,-1,sizeof h);
        idx=0;
        scnt=0;
        times=0;
        memset(dfn,0,sizeof dfn);
        memset(low,0,sizeof low);
        memset(in,0,sizeof in);
       // memset(id,0,sizeof id);
        for(i=1;i<=m;i++){
            int a,b;
            scanf("%d%d",&a,&b);
            add(a,b);
        }
        for(i=1;i<=n;i++){
            if(!dfn[i])
            tarjan(i);
        }
        for(i=1;i<=scnt;i++)
            g[i].clear();
        for(i=1;i<=n;i++){
            int j;
            for(j=h[i];j!=-1;j=ne[j]){
                int k=e[j];
                if(id[i]!=id[k]){
                    g[id[i]].push_back(id[k]);
                    in[id[k]]++;
                }
            }
        }
        if(!topo())
        cout<<"No"<<endl;
        else
        cout<<"Yes"<<endl;
    }
}