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#include<bits/stdc++.h>
#define inf 0x3f3f3f3f
#define atn 222222
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define f(i,a,b) for(int i = a;i <= b;++i)
using namespace std;
vector<int>v[1111];
bool ca[1111][1111],vis[1111];
signed main(){
	ios_base::sync_with_stdio(false);
	cin.tie(0);cout.tie(0);
	int T;
	cin>>T;
	while(T--){
		memset(ca,0,sizeof(ca));
		int n,m;
		cin>>n>>m;
		f(i,1,n)v[i].clear();
		f(i,1,m){
			int u,V;
			cin>>u>>V;
			v[u].pb(V);
		}f(i,1,n){
			memset(vis,0,sizeof(vis));
			queue<int>q;
			q.push(i);
			while(!q.empty()){
				int x=q.front();
				q.pop();
				vis[x]=1;
				ca[i][x]=ca[x][i]=1;
				for(auto y:v[x]){
					if(!vis[y])q.push(y);
				}
			}
		}bool ans=1;
		f(i,1,n){
			bool f=1;
			f(j,1,n)if(ca[i][j]==0){f=0;break;}
			if(!f){ans=0;break;}
		}if(ans)cout<<"Yes\n";
		else cout<<"No\n";
	}
	return 0;
	//十年OI一场空，define int 见祖宗。
	//十年OI一场空，不开long long见祖宗。
}
/*
----- ------- |     |  /---\
\      |   |  |     | /     \
 \     |   |  |     | |     |
 /     |   |  |     | |     |
/      |   |  \     / |     |
-----  |   |   \---/  |     |


    |                                      /---\     /|      /---\   ---
    |									. /     \   / |	    /     \ /   \
    | 									  |     |  /  |     |     |     /
--- |----| ----- |----| |----| \      / | |     | /___|____ |     |    /
  / |    | |   | |    | |    |  \    /  | |     |     |		|     |   /
/   |    | ----- |	  | |    |   \  /   | \     /     |		\     /  /
--- |    | |____ |	  | |----|    \/    |  \---/      |		 \---/  /----
							 |    /
							 |   /
						-----   /
*/