#include <bits/stdc++.h>
using namespace std;
bool compar(const pair<long, pair<long, long> >& a,
            const pair<long, pair<long, long> >& b) {
  return a.second.second < b.second.second;
}
int main() {
  int t;
  long j, n, i, x, y, k;
  bool flag = true;
  string ans = "";
  cin >> t;
  vector<pair<long, pair<long, long> > > p(1000);
  for (i = 0; i < t; i++) {
    cin >> n;
    for (j = 0; j < n; j++) {
      cin >> p[j].first;
      cin >> p[j].second.first;
    }
    for (j = 0; j < n; j++) {
      p[j].second.second =
          (p[j].first * p[j].first) + (p[j].second.first * p[j].second.first);
    }
    sort(p.begin(), p.begin() + n, compar);
    j = 0;
    x = 0;
    y = 0;
    while (j < n && x <= p[j].first && y <= p[j].second.first) {
      while (x < p[j].first) {
        x++;
        ans += 'R';
      }
      while (y < p[j].second.first) {
        y++;
        ans += 'U';
      }
      j++;
    }
    if (p[n - 1].first == x && p[n - 1].second.first == y) {
      cout << "YES" << endl;
      cout << ans << endl;
    } else
      cout << "NO" << endl;
    ans = "";
  }
  return 0;
}
