#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  long long int t;
  cin >> t;
  while (t--) {
    pair<long long int, long long int> p;
    long long int n;
    cin >> n;
    vector<pair<long long int, long long int>> v;
    while (n--) {
      cin >> p.first >> p.second;
      v.push_back(p);
    }
    sort(v.begin(), v.end());
    long long int m = v.begin()->second;
    n = v.begin()->first;
    int flag = 0;
    string ans;
    if (m < 0 || n < 0) {
      flag = 1;
      cout << "NO";
      goto abhi;
    }
    ans += string(n, 'R');
    ans += string(m, 'U');
    for (auto it = v.begin(); it < v.end() - 1; it++) {
      auto i = it + 1;
      m = i->second - it->second;
      n = i->first - it->first;
      if (m < 0 || n < 0) {
        flag = 1;
        cout << "NO";
        break;
      }
      ans += string(n, 'R');
      ans += string(m, 'U');
    }
    if (flag == 0) {
      cout << "YES\n" << ans;
    }
  abhi:
    cout << "\n";
  }
  return 0;
}
