#include <bits/stdc++.h>
using namespace std;
bool compare(pair<int, int> p1, pair<int, int> p2) {
  if (p1.first == p2.first)
    return p1.second < p2.second;
  else {
    return p1.first < p2.first;
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  int t;
  cin >> t;
  while (t--) {
    int n;
    cin >> n;
    vector<pair<int, int>> p;
    for (int i = 0; i < n; i++) {
      int u, v;
      cin >> u >> v;
      p.push_back(make_pair(u, v));
    }
    sort(p.begin(), p.end(), compare);
    bool ans = true;
    for (int i = 0; i < n - 1; i++) {
      if (p[i].second > p[i + 1].second) {
        ans = false;
        break;
      }
    }
    if (!ans) {
      cout << "NO" << endl;
      continue;
    }
    cout << "YES" << endl;
    pair<int, int> cur = {0, 0};
    string s = "";
    for (int i = 0; i < n; i++) {
      int u = p[i].first - cur.first;
      int v = p[i].second - cur.second;
      while (u--) {
        s += 'R';
      }
      while (v--) {
        s += 'U';
      }
      cur = p[i];
    }
    cout << s << endl;
  }
  return 0;
}
