#include <bits/stdc++.h>
using namespace std;
pair<long long, long long> pt[1005];
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0), cout.tie(0);
  int t;
  cin >> t;
  while (t--) {
    int n;
    cin >> n;
    pt[0] = {0ll, 0ll};
    for (int i = 1; i <= n; i++) cin >> pt[i].first >> pt[i].second;
    sort(pt, pt + n + 1);
    bool pepas = false;
    string s = "";
    for (int i = 1; i <= n; i++) {
      if (pt[i].second < pt[i - 1].second)
        pepas = true;
      else {
        for (int j = 0; j < pt[i].first - pt[i - 1].first; j++) s += 'R';
        for (int j = 0; j < pt[i].second - pt[i - 1].second; j++) s += 'U';
      }
    }
    if (pepas)
      cout << "NO\n";
    else {
      cout << "YES\n";
      cout << s << "\n";
    }
  }
  return 0;
}
