import collections


def main():
    t = int(input())

    for _ in range(t):
        d = collections.defaultdict(set)
        n, m = map(int, input().split())
        for _ in range(m):
            fr, to = map(int, input().split())
            d[fr].add(to)
            d[to].add(fr)

        lst = list(map(len, dict(d).values()))
        if len(lst) != len(set(lst)):
            print("YES")
        else:
            print("NO")


if __name__ == "__main__":
    main()