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