T = int(input())
for _ in range(T):
    N, L = map(int, input().split())
    x, y = [list(map((-1).__add__, i)) for i in zip(*[list(map(int, input().split())) for _ in range(N)])]
    print(len(x))
    for i in range(len(x)):
        print(x[i], y[i])