#include <bits/stdc++.h>
using namespace std;
bool myComparison(const pair<int, int> &a, const pair<int, int> &b) {
  return a.second < b.second;
}
int main() {
  long long int t;
  cin >> t;
  while (t--) {
    long long int n;
    cin >> n;
    vector<pair<long long int, long long int>> v;
    for (auto i = 0; i < n; i++) {
      long long int x, y;
      cin >> x >> y;
      v.push_back({x, y});
    }
    sort(v.begin(), v.end());
    for (auto i = 0; i < v.size(); i++) {
      long long int start = i, end = v.size() - 1, u = 0;
      for (auto j = i; j < v.size(); j++) {
        if (v[j].first == v[i].first)
          ;
        else {
          u = 1;
          end = j - 1;
          break;
        }
      }
      sort(v.begin() + start, v.begin() + end + 1, myComparison);
      i = end;
    }
    long long int x = 0, y = 0, u = 0;
    for (auto i = 0; i < v.size(); i++) {
      if (v[i].first >= x && v[i].second >= y) {
        x = v[i].first;
        y = v[i].second;
      } else {
        u = 1;
        break;
      }
    }
    if (u) {
      cout << "NO\n";
      continue;
    }
    x = 0, y = 0;
    cout << "YES\n";
    for (auto i = 0; i < v.size(); i++) {
      for (auto j = 0; j < (v[i].first - x); j++) cout << "R";
      x = v[i].first;
      for (auto j = 0; j < v[i].second - y; j++) cout << "U";
      y = v[i].second;
    }
    cout << "\n";
  }
  return 0;
}
