#include <bits/stdc++.h>
#define bit(x) (1LL << (x))
using namespace std;
const int N = 1e5 + 3;
int T;
int n, num, m, x, y;


void work(){
	cin >> n >> m;
	vector<vector<pair <int,int>>> g(n);
	vector <pair <int,int>> e;
	for(int i = 0; i < m; ++i){
		cin >> x >> y;
		x -= 1;y -= 1;
		g[x].push_back({y,i});
		g[y].push_back({x,i});
		e.push_back({x,y});
	}
	vector <array <int,20>> prt(n);
	vector <int> dep(n),vis(m),dfn(n);
	auto dfs = [&] (auto &&self,int u,int fa) -> void{
		for(auto [v,w] : g[u]) if(!dfn[v]) {
			prt[v][0] = u;
			vis[w] = 1;
			dfn[v] = 1;
			dep[v] = dep[u] + 1;
			for(int i = 1;i < 20;i++) prt[v][i] = prt[prt[v][i - 1]][i - 1];
			self(self,v,u);
		}
	};
	dfn[0] = 1;
	dfs(dfs,0,-1);
	auto LCA = [&] (int u,int v) {
		if(dep[u] < dep[v]) swap(u,v);
		int d = dep[u] - dep[v];
		for(int i = 19;i >= 0;i--) if(bit(i) & d) {
			u = prt[u][i];
		}
		if(u == v) return u;
		for(int i = 19;i>= 0;i--) if(prt[u][i] != prt[v][i]) {
			u = prt[u][i];
			v = prt[v][i];
		}
		return prt[u][0];
	};
	
	vector <int> col(n);
	
	auto color = [&] (int u,int lca) {
		while(u != lca) {
			if(col[u]) return false;
			col[u] = 1;
			u = prt[u][0];
		}	
		return true;
	};
	
	for(int i = 0;i < m;i++) if(!vis[i]) {
		auto [u,v] = e[i];
		int lca = LCA(u,v);
		if(dep[u] + dep[v] - dep[lca] * 2 == 3) {
			if((!color(u,lca)) || (!color(v,lca))) {
				cout << "NO\n";
				return;
			}
		}else {
			cout << "NO\n";
			return;
		}
	}
	cout << "YES\n";
}


int main(){
//	freopen("test.txt", "r", stdin);
	ios::sync_with_stdio(false);
	cin.tie(0);
	cin >> T;
	while(T--){
		work();
	}	
	return 0;
}