#include<bits/stdc++.h>
using namespace std;
const int N=1e5+5,E=N<<1;
typedef unsigned long long ull;
int read(){
	int red=0,f=1;char ch=getchar();
	while(ch<'0'||ch>'9'){ if(ch=='-') f=-f;ch=getchar();}
	while(ch>='0'&&ch<='9') red=red*10+ch-48,ch=getchar();
	return red*f;
}
int T,n,m;
int son[E],nxt[E],lnk[N],tot;
void add_e(int x,int y){
    son[++tot]=y,nxt[tot]=lnk[x],lnk[x]=tot;
}
int fa[N];bool vis[N],isH[N],findH;
#define v son[j]
void find(int x){
    vis[x]=1;
    for(int j=lnk[x];j&&!findH;j=nxt[j]) {
        if(!vis[v]){
            fa[v]=x;find(v);
        }else if(v^fa[x]){
            for(;x!=v;x=fa[x]) isH[x]=1;
            isH[v]=1;findH=1;
            return;
        }
    }
}
const ull mask=mt19937_64(time(nullptr))();
ull shift(ull x) {
    x ^= mask;
    x ^= x << 13;
    x ^= x >> 7;
    x ^= x << 17;
    x ^= mask;
    return x;
}
ull hsh[N],HASH;bool flg;
void getHash(int x,int p=0){
    hsh[x]=1;
    for(int j=lnk[x];j;j=nxt[j]) if(v!=p&&!isH[v]){
        getHash(v,x);
        hsh[x]+=shift(hsh[v]);
    }
}
void clear(){
    memset(lnk,0,sizeof(int)*(n+1));
    memset(vis,0,sizeof(bool)*(n+1));
    memset(isH,0,sizeof(bool)*(n+1));
    tot=flg=findH=0;
}
int main(){
    T=read();
    while(T--){
        clear();n=read(),m=read();
        for(int i=1;i<=m;i++){
            int x=read(),y=read();
            add_e(x,y),add_e(y,x);
        }
        if(m==n-1) puts("YES");else
        if(m>n) puts("NO");else{
            find(1);bool ok=1;
            for(int i=1;i<=n;i++) if(isH[i]){
                getHash(i);
                if(!flg) flg=1,HASH=hsh[i];
                if(HASH!=hsh[i]) ok=0;
            }
            puts(ok?"YES":"NO");
        }
    }
    return 0;
}