#include <bits/stdc++.h>
using namespace std;
template <class A, class B>
ostream& operator<<(ostream& out, const pair<A, B>& a) {
  return out << "(" << a.first << ", " << a.second << ")";
}
template <int>
ostream& operator<<(ostream& os, const vector<int>& v) {
  os << "[";
  for (int i = 0; i < v.size(); ++i) {
    if (v[i] != 1000000001)
      os << v[i];
    else
      os << "INF";
    if (i != v.size() - 1) os << ", ";
  }
  os << "]\n";
  return os;
}
template <typename T>
ostream& operator<<(ostream& os, const vector<T>& v) {
  os << "[";
  for (int i = 0; i < v.size(); ++i) {
    os << v[i];
    ;
    if (i != v.size() - 1) os << ", ";
  }
  os << "]\n";
  return os;
}
int main() {
  {
    ios::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
  };
  int t;
  cin >> t;
  while (t--) {
    int n;
    cin >> n;
    vector<pair<int, int> > v(n + 1);
    v[0] = make_pair(0, 0);
    for (int i = 1; i <= n; i++) {
      cin >> v[i].second >> v[i].first;
    }
    sort(v.begin(), v.end());
    int first = v[0].second;
    bool boo = true;
    for (int i = 0; i < v.size(); i++) {
      if (v[i].second < first) {
        boo = false;
        break;
      }
      first = v[i].second;
    }
    if (!boo)
      cout << "NO" << endl;
    else {
      cout << "YES" << endl;
      for (int i = 1; i < v.size(); i++) {
        for (int j = 0; j < v[i].second - v[i - 1].second; j++) cout << "R";
        for (int j = 0; j < v[i].first - v[i - 1].first; j++) cout << "U";
      }
      cout << endl;
    }
  }
  return 0;
}
