T = int(input())
for _ in range(T):
    N, M = map(int, input().split())
    G = [0] * N
    for i in range(M):
        u, v = map(int, input().split())
        G[u-1] += 1
        G[v-1] += 1
    S = set()
    for i in range(N):
        S.add(G[i])
    print("Yes") if len(S) != N else print("No")