#include <bits/stdc++.h>
using namespace std;
bool sortinrev(long long x, long long y) { return x > y; }
void swap(long long* a, long long* b) {
  long long temp = *a;
  *a = *b;
  *b = temp;
}
long long div_ceil(long long a, long long b) { return (a + b - 1) / b; }
long long gcd(long long a, long long b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
const int MOD = 1000 * 1000 * 1000 + 7;
const long long INF = 1e18L + 5;
const int nax = 1000005;
const int N = int(1e6);
void solve() {
  long long n;
  cin >> n;
  long long prevP, prevC;
  bool flag = 1;
  cin >> prevP >> prevC;
  if (prevC > prevP) flag = 0;
  for (long long i = 1; i < n; i++) {
    long long x, y;
    cin >> x >> y;
    if (prevC > y || prevP > x || x < y) flag = 0;
    if (y - prevC > x - prevP) flag = 0;
    prevP = x;
    prevC = y;
  }
  if (flag)
    cout << "YES\n";
  else
    cout << "NO\n";
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long t = 1;
  cin >> t;
  while (t--) {
    solve();
  }
  cerr << "\nTime elapsed: " << 1000 * clock() / CLOCKS_PER_SEC << "ms\n";
  return 0;
}
