#include <bits/stdc++.h>
using namespace std;
string str = "";
void disp(char c, int n) {
  for (int i = 1; i <= n; i++) str += c;
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int n, x, y;
  int t;
  cin >> t;
  while (t--) {
    cin >> n;
    vector<pair<int, int>> vect;
    for (int i = 0; i < n; i++) {
      cin >> x >> y;
      vect.push_back(make_pair(x, y));
      sort(vect.begin(), vect.end());
    }
    int xprev = 0, yprev = 0;
    bool flag = 1;
    for (pair<int, int> p : vect) {
      if (p.first - xprev < 0 || p.second - yprev < 0) flag = 0;
      if (p.first - xprev > 0) disp('R', p.first - xprev);
      if (p.second - yprev > 0) disp('U', p.second - yprev);
      xprev = p.first;
      yprev = p.second;
    }
    if (flag == 1)
      cout << "YES" << endl << str << endl;
    else
      cout << "NO" << endl;
    str = "";
  }
  return 0;
}
