T = int(input())

for _ in range(T):
    N, L = map(int, input().split())
    XY = [list(map(int, input().split())) for _ in range(N)]
    RANGE = L//N+1
    qS = [[] for _ in range(L//RANGE+1)]
    for i in range(N):
        X, Y = XY[i]
        qS[X//RANGE].append((X, Y))
    for i in range(L//RANGE+1):
        qS[i].sort(key=lambda x:x[1], reverse=i%2)
    ans = []
    for q in qS:
        for x, y in q:
            ans.append((x, y))
    print(len(ans))
    for a in ans:
        print(*a)