for _ in range(int(input())):
    n, m = map(int, input().split())
    G = [[] for i in range(n)]
    for _ in range(m):
        u, v = map(int, input().split())
        G[u - 1].append(v - 1)
        G[v - 1].append(u - 1)
    s = set([len(G[i]) for i in range(n)])
    print("Yes" if n - len(s) else "No")