#include <bits/stdc++.h>
using namespace std;
inline int read() {
  int x = 0, f = 1;
  char ch = getchar();
  while (ch < '0' || ch > '9') {
    f = ch == '-' ? -1 : 1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9') x = x * 10 + ch - '0', ch = getchar();
  return x * f;
}
const int N = 105;
int n, p[N], c[N];
int main() {
  int T = read();
  while (T--) {
    n = read();
    for (int i = 1; i <= n; i++) p[i] = read(), c[i] = read();
    p[0] = 0;
    c[0] = 0;
    int fl = 1;
    for (int i = 1; i <= n; i++) {
      if (c[i] < c[i - 1] || p[i] < p[i - 1]) {
        fl = 0;
        break;
      }
      if (c[i] - c[i - 1] > p[i] - p[i - 1]) {
        fl = 0;
        break;
      }
    }
    if (fl)
      puts("YES");
    else
      puts("NO");
  }
}
