#include <bits/stdc++.h>
using namespace std;
void err(istream_iterator<string> it) {}
template <typename T, typename... Args>
void err(istream_iterator<string> it, T a, Args... args) {
  cerr << *it << " = " << a << " ";
  err(++it, args...);
}
signed main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long int t = 1;
  cin >> t;
  while (t--) {
    long long int n;
    cin >> n;
    long long int pp, pc, sump = 0, sumc = 0;
    cin >> pp >> pc;
    sump += pp;
    sumc += pc;
    bool pass = true;
    if (sump < sumc) pass = false;
    for (long long int i = 1, p, c; i < n; i++) {
      cin >> p >> c;
      sump += p;
      sumc += c;
      if (p < pp || (p - pp < c - pc) || (c < pc)) {
        pass = false;
      }
      pp = p;
      pc = c;
    }
    cout << (pass ? "YES" : "NO") << '\n';
  }
  return 0;
}
