#include <bits/stdc++.h>
using namespace std;
int main() {
  int t, n;
  cin >> t;
  while (t--) {
    cin >> n;
    int p, c, p_p, p_c;
    bool ans = true;
    cin >> p >> c;
    if (p < c) {
      ans = false;
    }
    p_p = p, p_c = c;
    for (int i = 1; i < n; ++i) {
      cin >> p >> c;
      if (p < c || p < p_p || c < p_c || (c - p_c) > (p - p_p)) {
        ans = false;
      }
      p_p = p;
      p_c = c;
    }
    if (ans) {
      cout << "Yes"
           << "\n";
    } else {
      cout << "No"
           << "\n";
    }
  }
}
