#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  for (int i = 0; i < n; ++i) {
    int k;
    cin >> k;
    bool ok = true;
    int pa = 0, pb = 0;
    for (int j = 0; j < k; ++j) {
      int a, b;
      cin >> a >> b;
      if (a < pa || b < pb) ok = false;
      if (a == pa && b != pb) ok = false;
      if (a > pa && (a - pa) < (b - pb)) ok = false;
      pa = a;
      pb = b;
    }
    cout << (ok ? "YES" : "NO") << endl;
  }
}
