#include <bits/stdc++.h>
using namespace std;
bool sortbysec(const pair<int, int> &a, const pair<int, int> &b) {
  return (a.second < b.second);
}
int main() {
  int T, i, j, t, k, x, y, n, f;
  cin >> T;
  for (t = 0; t < T; t++) {
    vector<pair<int, int>> points;
    string s = "";
    f = 0;
    cin >> n;
    for (i = 0; i < n; i++) {
      cin >> x >> y;
      points.push_back(make_pair(x, y));
    }
    sort(points.begin(), points.end());
    j = points[0].first;
    k = points[0].second;
    while (j > 0) {
      s = s + 'R';
      j--;
    }
    while (k > 0) {
      s = s + 'U';
      k--;
    }
    for (i = 1; i < n; i++) {
      j = points[i].first - points[i - 1].first;
      k = points[i].second - points[i - 1].second;
      if (j < 0 || k < 0) {
        f = 1;
        break;
      }
      while (j > 0) {
        s = s + 'R';
        j--;
      }
      while (k > 0) {
        s = s + 'U';
        k--;
      }
    }
    if (f) {
      cout << "NO" << endl;
    } else {
      cout << "YES" << endl;
      cout << s << endl;
    }
  }
  return 0;
}
