#include <bits/stdc++.h>
using namespace std;
const int MAXN = 103;
int p[MAXN], c[MAXN];
int main() {
  int t;
  cin >> t;
  while (t--) {
    int n;
    cin >> n;
    bool check = true;
    for (int i = 1; i <= n; i++) {
      cin >> p[i] >> c[i];
      if (c[i] > p[i] || c[i] < c[i - 1] || p[i] < c[i] ||
          p[i] - p[i - 1] < c[i] - c[i - 1])
        check = false;
    }
    if (check)
      cout << "YES"
           << "\n";
    else
      cout << "NO"
           << "\n";
  }
}
