#include <bits/stdc++.h>
using namespace std;
int main() {
  int t;
  cin >> t;
  while (t--) {
    int n;
    cin >> n;
    pair<int, int> p[n];
    for (int i = 0; i < n; i++) {
      cin >> p[i].first >> p[i].second;
    }
    bool check = true;
    for (int i = 0; i < n; i++) {
      if (p[i].first < p[i].second) check = false;
      if (i > 0) {
        if (p[i].first == p[i - 1].first) {
          if (p[i].second != p[i - 1].second) check = false;
        } else if (p[i].first > p[i - 1].first) {
          if (p[i].second < p[i - 1].second) check = false;
        } else
          check = false;
        if (p[i].first - p[i - 1].first < p[i].second - p[i - 1].second)
          check = false;
      }
    }
    if (check)
      cout << "YES\n";
    else
      cout << "NO\n";
  }
  return 0;
}
