#include <bits/stdc++.h>
using std::cin;
using std::cout;
using std::string;
int main() {
  int t = 0;
  cin >> t;
  for (int i = 0; i < t; ++i) {
    int n = 0;
    cin >> n;
    bool res = true;
    int p_pr = 0;
    int c_pr = 0;
    if (n > 0) {
      cin >> p_pr >> c_pr;
    }
    if (c_pr > p_pr) {
      res = false;
    }
    for (int j = 1; j < n; ++j) {
      int p = 0;
      int c = 0;
      cin >> p >> c;
      if (p < p_pr) {
        res = false;
      }
      if (c < c_pr) {
        res = false;
      }
      if (p - c < p_pr - c_pr) {
        res = false;
      }
      p_pr = p;
      c_pr = c;
    }
    if (res) {
      cout << "YES\n";
    } else {
      cout << "NO\n";
    }
  }
  return 0;
}
