#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, t;
  cin >> t;
  while (t--) {
    cin >> n;
    vector<pair<int, int> > a(n);
    for (int i = 0; i < n; i++) {
      cin >> a[i].first >> a[i].second;
    }
    sort(a.begin(), a.end());
    bool flag = true;
    string ans = "";
    int curx = 0, cury = 0;
    for (int i = 0; i < n; i++) {
      for (int j = i + 1; j < n; j++) {
        if (a[j].first > a[i].first && a[j].second < a[i].second) {
          flag = false;
          break;
        }
      }
      if (flag) {
        while (curx < a[i].first) {
          ans = ans + "R";
          curx++;
        }
        while (cury < a[i].second) {
          ans = ans + "U";
          cury++;
        }
      } else {
        break;
      }
    }
    if (flag) {
      cout << "YES" << endl << ans << endl;
    } else
      cout << "NO" << endl;
  }
  return 0;
}
