#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define MP make_pair
mt19937 rnd(time(0));
const int MAXN=1e5+5;
const int MOD=998244353;
int n,m,a[MAXN];
vector<int> edg[MAXN];
ll val[MAXN],hs[MAXN],d[MAXN],dep[MAXN];
void solve(){
	cin>>n>>m;
	for(int i=1;i<=n;i++) edg[i].clear(),hs[i]=1,dep[i]=0;
	for(int i=1,u,v;i<=m;i++){
		cin>>u>>v;
		edg[u].push_back(v);
		edg[v].push_back(u);
	}
	for(int i=1;i<=n;i++) d[i]=edg[i].size();
	if(m==n-1){cout<<"YES"<<endl;return;}
	if(m>n){cout<<"NO"<<endl;return;} 
	queue<int> q;
	for(int i=1;i<=n;i++) if(d[i]==1) q.push(i);
	while(!q.empty()){
		int u=q.front();q.pop();
		hs[u]=(hs[u]+val[dep[u]])%MOD;
//		cout<<u<<' '<<hs[u]<<endl;
		for(int v:edg[u]){
			if(d[v]<=1) continue;
			hs[v]=hs[v]*hs[u]%MOD;
			dep[v]=max(dep[v],dep[u]);
			if(--d[v]==1) q.push(v);
		} 
	}
	ll tot=-1;
	for(int i=1;i<=n;i++) if(d[i]>=2){
		if(tot==-1) tot=hs[i];
		else if(tot!=hs[i]){cout<<"NO"<<endl;return;} 
	}
	cout<<"YES"<<endl;
}
int main(){
	ios::sync_with_stdio(false);
	for(int i=0;i<MAXN;i++) val[i]=rnd()%MOD;
	int _;cin>>_;
	while(_--) solve();
}