#include"bits/stdc++.h"

 #define db double

 #define ll long long

 #define vl vector<ll>

 #define ci(x) scanf("%d",&x)

 #define cd(x) scanf("%lf",&x)

 #define cl(x) scanf("%lld",&x)

 #define pi(x) printf("%d\n",x)

 #define pd(x) printf("%f\n",x)

 #define pl(x) printf("%lld\n",x)

 #define rep(i, a, n) for (int i=a;i<n;i++)

 #define per(i, a, n) for (int i=n-1;i>=a;i--)

 #define fi first

 #define se second

 using namespace std;

 typedef pair<int, int> pii;

 const int N = 6e3 + ;

 const int mod = 1e9 + ;

 const int MOD = ;

 const db PI = acos(-1.0);

 const db eps = 1e-;

 const int inf = 0x3f3f3f3f;

 const ll INF = 0x3fffffffffffffff;

 int in[N];

 int out[N];

 int head[N],h[N];

 int low[N],dfn[N];

 int ins[N],beg[N];

 int cnt,id,num,cntt;

 int n, m, t;

 queue<int> q;

 stack<int> s;

 struct P {

     int to, nxt;

 } e[ * N], g[ * N];

 void add(int u, int v) {//原图

     e[cnt].to = v;

     e[cnt].nxt = head[u];

     head[u] = cnt++;

 }

 void ADD(int u, int v) {//缩点图

     g[cntt].to = v;

     g[cntt].nxt = h[u];

     h[u] = cntt++;

 }

 void tarjan(int u)

 {

     low[u]=dfn[u]=++id;

     ins[u]=;

     s.push(u);

     for(int i=head[u];~i;i=e[i].nxt){

         int v=e[i].to;

         if(!dfn[v]) tarjan(v),low[u]=min(low[u],low[v]);

         else if(ins[v]) low[u]=min(low[u],dfn[v]);

     }

     if(low[u]==dfn[u]){

         int v;

         do{

             v=s.top();s.pop();

             beg[v]=num;

             ins[v]=;

         }while(u!=v);

         num++;

     }

 }

 bool work()

 {

     while(!q.empty()) q.pop();

     for(int i=;i<num;i++){

         if(!in[i]) q.push(i);

 //        if(in[i]>1||out[i]>1) return 0;//链上点出度入度都不大于1

     }

     int ans=;

     while(!q.empty()){

         if(q.size()>) return ;

         int u=q.front();q.pop();

         ans++;

         for(int i=h[u];~i;i=g[i].nxt){

             int v=g[i].to;

             in[v]--;

             if(!in[v]) q.push(v);

         }

     }

     return ans==num;//成链

 }

 void init()

 {

     cnt = num = id = cntt= ;

     memset(in, , sizeof(in));

     memset(out, , sizeof(out));

     memset(head, -, sizeof(head));

     memset(h, -, sizeof(h));

     memset(low,, sizeof(low));

     memset(dfn,, sizeof(dfn));

     memset(ins,, sizeof(ins));

     memset(beg,, sizeof(beg));

 }

 int main() {

     ci(t);

     while(t--)

     {

         ci(n),ci(m);

         init();

         for (int i = ; i < m; i++) {

             int x, y;

             ci(x), ci(y);

             add(x, y);

         }

         for(int i=;i<=n;i++) if(!dfn[i]) tarjan(i);

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

             for(int j=head[i];~j;j=e[j].nxt){

                 int v=e[j].to;

                 if(beg[i]!=beg[v]) out[beg[i]]++,in[beg[v]]++,ADD(beg[i],beg[v]);//缩点后的图

             }

         }

         puts(work()?"Yes":"No");

     }

 }