#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  ;
  int t;
  cin >> t;
  while (t--) {
    int n;
    cin >> n;
    pair<int, int> arr[n];
    bool fg = 0;
    for (int i = 0; i < n; ++i) {
      cin >> arr[i].first >> arr[i].second;
      if (arr[i].second > arr[i].first) fg = 1;
      if (i == 0) continue;
      if (arr[i].second > arr[i].first) fg = 1;
      if (arr[i].first < arr[i - 1].first || arr[i].second < arr[i - 1].second)
        fg = 1;
      int maxch = arr[i].first - arr[i - 1].first;
      if (arr[i].second > arr[i - 1].second + maxch) fg = 1;
    }
    if (fg) {
      cout << "NO\n";
    } else {
      cout << "YES\n";
    }
  }
  return 0;
}
