#include <bits/stdc++.h>
using namespace std;
pair<int, int> p[1005];
int main() {
  int q;
  cin >> q;
  int n;
  while (q--) {
    cin >> n;
    int x, y;
    for (int i = 0; i < n; i++) {
      cin >> x >> y;
      p[i].first = x;
      p[i].second = y;
    }
    sort(p, p + n);
    x = 0;
    y = 0;
    bool q1 = true;
    for (int i = 0; i < n - 1; i++) {
      if (p[i + 1].first < p[i].first || p[i + 1].second < p[i].second) {
        cout << "NO";
        q1 = false;
        break;
      }
    }
    if (q1) {
      cout << "YES\n";
      x = p[0].first;
      y = p[0].second;
      while (x--) cout << "R";
      while (y--) cout << "U";
      for (int i = 0; i < n - 1; i++) {
        x = p[i + 1].first - p[i].first;
        y = p[i + 1].second - p[i].second;
        while (x--) cout << "R";
        while (y--) cout << "U";
      }
    }
    cout << "\n";
  }
}
