#include <bits/stdc++.h>
using namespace std;
const int dx[4] = {0, 0, -1, 1};
const int dy[4] = {-1, 1, 0, 0};
int main() {
  int i, j, k, n;
  long int mx, mn, sm = 0;
  int t;
  cin >> t;
  while (t--) {
    int f = 0;
    cin >> n;
    vector<pair<int, int>> v(n);
    for (i = 0; i < n; i++) {
      int a, b;
      cin >> a >> b;
      v[i] = (make_pair(a, b));
    }
    if (v[0].first < v[0].second) f = 1;
    for (i = 1; i < n; i++) {
      int x = v[i].first - v[i - 1].first;
      int y = v[i].second - v[i - 1].second;
      if (x < 0 || y < 0 || (v[i].first < v[i].second) ||
          (v[i - 1].first < v[i - 1].second) || y > x) {
        f = 1;
        break;
      }
    }
    if (f)
      cout << "NO"
           << "\n";
    else {
      cout << "YES"
           << "\n";
    }
  }
}
