#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using i2 = pair<int, int>;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  int T;
  cin >> T;
  while (T--) {
    int n;
    cin >> n;
    int pp = 0, pc = 0;
    bool ok = true;
    for (int i = 1; i <= n; i++) {
      int np, nc;
      cin >> np >> nc;
      if (np - pp < nc - pc || nc - pc < 0) ok = false;
      pp = np;
      pc = nc;
    }
    cout << (ok ? "YES\n" : "NO\n");
  }
  return 0;
}
