package DataStructures.Graphs;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;

/**
 * Given an adjacency list of a graph adj  of V no. 
 * of vertices having 0 based index. 
 * Check whether the graph is bipartite or not.
 * 
 * Input : 
 * {{0, 1, 0, 1},
 *  {1, 0, 1, 0},
 *  {0, 1, 0, 1},
 *  {1, 0, 1, 0}}
 * 
 * Output : YES
 */
public class BipartiteGrapfDFS {
    private static boolean bipartite(int V, ArrayList<ArrayList<Integer>>adj, int[] color, int node){
        if(color[node] == -1){
            color[node] = 1;
        }
        for(Integer it : adj.get(node)){
            if(color[it] == -1){
                color[it] = 1-color[node];
                if(bipartite(V, adj, color, it)== false) return false;
            }
            else if(color[it] == color[node]){
                return false;
            }
        }
        return true;
    }
    public static boolean isBipartite(int V, ArrayList<ArrayList<Integer>> adj)
    {
        // Code here
        int[] color = new int[V+1];
        Arrays.fill(color, -1);
        
        for(int i =0; i< V; i++){
            if(color[i] == -1){
                if(!bipartite(V, adj, color, i)){
                    return false;
                }
            }
        }
        return true;
    }
    public static void main(String[] args) throws IOException {
        BufferedReader read = new BufferedReader(new InputStreamReader(System.in));
        int t = Integer.parseInt(read.readLine().trim());
        while(t-- > 0) {
            String[] S = read.readLine().trim().split(" ");
            int V = Integer.parseInt(S[0]);
            int E = Integer.parseInt(S[1]);
            
            ArrayList<ArrayList<Integer>> adj = new ArrayList<>();
            for(int i =0;i < V; i++) {
                adj.add(new ArrayList<>());
            }
            for(int i = 0; i < E; i++) {
                String[] s = read.readLine().trim().split(" ");
                int u = Integer.parseInt(s[0]);
                int v = Integer.parseInt(s[1]);
                adj.get(u).add(v);
                adj.get(v).add(u);
            }
            
            boolean ans = isBipartite(V, adj);
            if(ans)
                System.out.println("YES");
            else
                System.out.println("NO");
        }
    }
}