#include <bits/stdc++.h>
using namespace std;
pair<int, int> x[1024], y[1024];
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int t;
  cin >> t;
  while (t--) {
    int n;
    cin >> n;
    for (int i = 0; i < n; i++) {
      cin >> x[i].first >> x[i].second;
      y[i].first = x[i].first;
      y[i].second = x[i].second;
    }
    sort(x, x + n, [](const pair<int, int>& a, const pair<int, int>& b) {
      return a.first < b.first || (a.first == b.first && a.second < b.second);
    });
    sort(y, y + n, [](const pair<int, int>& a, const pair<int, int>& b) {
      return a.second < b.second || (a.second == b.second && a.first < b.first);
    });
    string ans = "";
    int r = 0, c = 0;
    for (int i = 0; i < n; i++) {
      if (x[i] != y[i]) {
        cout << "NO" << endl;
        ans = "";
        break;
      } else {
        ans += string(x[i].first - r, 'R');
        ans += string(x[i].second - c, 'U');
        r = x[i].first;
        c = x[i].second;
      }
    }
    if (!ans.empty()) {
      cout << "YES" << endl << ans << endl;
    }
  }
  return 0;
}
