#include <bits/stdc++.h>
using namespace std;
int main() {
  int test;
  cin >> test;
  while (test--) {
    int pkg;
    cin >> pkg;
    int yes = 1;
    string path = "";
    int rx, ry;
    rx = ry = 0;
    set<long int> s;
    for (int i = 0; i < pkg; i++) {
      int x, y;
      cin >> x >> y;
      s.insert((x * 10000) + y);
    }
    for (long int k : s) {
      int x, y;
      x = k / 10000;
      y = k % 10000;
      while (rx < x) {
        path += "R";
        rx++;
      }
      if (rx > x) {
        cout << "NO";
        yes = 0;
        break;
      }
      while (ry < y) {
        path += "U";
        ry++;
      }
      if (ry > y) {
        cout << "NO";
        yes = 0;
        break;
      }
    }
    if (yes) {
      cout << "YES\n" + path;
    }
    cout << endl;
  }
  return 0;
}
