def main():
    for _ in range(int(input())):
        N, M = map(int, input().split())
        degrees = [0] * N
        for _ in range(M):
            dep, dest = map(int, input().split())
            degrees[dep-1] += 1
            degrees[dest-1] += 1

        if len(degrees) != len(set(degrees)):
            print("Yes")
        else:
            print("No")


if __name__ == "__main__":
    main()