#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  int t;
  cin >> t;
  for (int ti = 0; ti < t; ti++) {
    int n;
    cin >> n;
    tuple<int, int> points[n];
    for (int i = 0; i < n; i++) {
      int x, y;
      cin >> x >> y;
      points[i] = make_tuple(x, y);
    }
    sort(points, points + n);
    int currentY = 0;
    bool ok = true;
    for (int i = 0; i < n; i++) {
      if (get<1>(points[i]) < currentY) {
        ok = false;
        break;
      }
      currentY = get<1>(points[i]);
    }
    if (!ok) {
      cout << "NO" << endl;
      continue;
    }
    cout << "YES" << endl;
    vector<char> ans;
    int currentX = 0;
    currentY = 0;
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < get<0>(points[i]) - currentX; j++) ans.push_back('R');
      for (int j = 0; j < get<1>(points[i]) - currentY; j++) ans.push_back('U');
      currentX = get<0>(points[i]);
      currentY = get<1>(points[i]);
    }
    for (int i = 0; i < ans.size(); i++) {
      cout << ans[i];
    }
    cout << endl;
  }
}
