#include <bits/stdc++.h>
using namespace std;
long long t, n, p, c, prep, prec;
bool ok = 1;
int main() {
  ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  cin >> t;
  while (t--) {
    cin >> n;
    ok = 1;
    prep = 0;
    prec = 0;
    for (int i = 0; i < n; i++) {
      cin >> p >> c;
      if (p < prep) ok = 0;
      if (c < prec) ok = 0;
      if ((c - prec) > (p - prep)) ok = 0;
      prep = p;
      prec = c;
    }
    if (ok)
      cout << "YES" << endl;
    else
      cout << "NO" << endl;
  }
}
