import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int t = sc.nextInt();
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < t; i++) {
            int n = sc.nextInt();
            int m = sc.nextInt();
            int[] counts = new int[n];
            for (int j = 0; j < m; j++) {
                counts[sc.nextInt() - 1]++;
                counts[sc.nextInt() - 1]++;
            }
            Arrays.sort(counts);
            boolean exist = false;
            for (int j = 0; j < n - 1 && !exist; j++) {
                exist = (counts[j] == counts[j + 1]);
            }
            if (exist) {
                sb.append("Yes");
            } else {
                sb.append("No");
            }
            sb.append("\n");
        }
        System.out.print(sb);
    }
}


class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public String next() throws Exception {
        if (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
}