T=int(input())
ans=""
for _ in range(T):
	n,m=map(int,input().split())
	g=[[] for _ in range(n+1)]
	for _ in range(m):
		u,v=map(int,input().split())
		g[u].append(v)
	for i in range(1,n+1):
		if len(ans)>=1000:print(ans);ans=""
		ans+=" ".join(map(str,sorted(g[i])))+"\n"
print(ans)