#include <bits/stdc++.h>
using namespace std;
const long long mod = 1000000007;
long long powmod(long long a, long long b) {
  long long res = 1;
  a %= mod;
  assert(b >= 0);
  for (; b; b >>= 1) {
    if (b & 1) res = res * a % mod;
    a = a * a % mod;
  }
  return res;
}
long long gcd(long long a, long long b) { return b ? gcd(b, a % b) : a; }
int t;
int n;
int x, y;
int main() {
  scanf("%d", &t);
  while (t--) {
    scanf("%d", &n);
    scanf("%d%d", &x, &y);
    bool f = false;
    int prex = x, prey = y;
    if (x < y) f = true;
    for (int i = 1; i < n; i++) {
      scanf("%d%d", &x, &y);
      if (x < y) f = true;
      if (x >= prex && y < prey) f = true;
      if (x < prex) f = true;
      int maxx = x - prex + prey;
      if (x >= prex && y > maxx) f = true;
      prex = x;
      prey = y;
    }
    if (f)
      printf("NO\n");
    else
      printf("YES\n");
  }
  return 0;
}
