import sys
input = sys.stdin.readline
T = int(input())
for _ in range(T):
    N, L = map(int, input().split())
    XY = [list(map(int, input().split())) for _ in range(N)]
    for i in range(N):
        x, y = XY[i]
        XY[i] = [x, y, x+y]
    XY.sort(key=lambda x:x[2])
    ans = []
    for x, y, _ in XY:
        ans.append((x, y))
    print(len(ans))
    for a in ans:
        print(*a)