#include <bits/stdc++.h>
using namespace std;
signed main() {
  std ::ios_base ::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  long long t;
  cin >> t;
  while (t--) {
    long long n, flag = 0;
    string s = "";
    cin >> n;
    vector<pair<long long, long long>> v(n);
    for (long long i = 0; i < n; i++) {
      long long x, y;
      cin >> x >> y;
      v[i] = {x, y};
    }
    sort(v.begin(), v.end());
    s += string(v[0].first, 'R') + string(v[0].second, 'U');
    for (long long i = 1; i < n; i++) {
      if (v[i - 1].second > v[i].second) {
        flag = 1;
        break;
      } else if (v[i - 1].first != v[i].first)
        s += string((v[i].first) - (v[i - 1].first), 'R') +
             string((v[i].second) - (v[i - 1].second), 'U');
      else
        s += string((v[i].second) - (v[i - 1].second), 'U');
    }
    if (flag == 1)
      cout << "NO\n";
    else {
      cout << "YES\n";
      cout << s << "\n";
    }
  }
}
