#include <bits/stdc++.h>
using namespace std;
void solve() {
  int n, x, y, cnt = 0;
  cin >> n;
  vector<int> adj[1000 + 1];
  set<int> s;
  for (int i = 0; i < n; i++) {
    cin >> x >> y;
    adj[x].push_back(y);
    s.insert(x);
  }
  string p = "";
  x = 0, y = 0;
  bool f = true;
  for (auto it = s.begin(); it != s.end(); it++) {
    int temp2 = *it - x;
    x = *it;
    for (int i = 0; i < temp2; i++) p += 'R';
    int mx = 0, cur = 0, temp = 0;
    for (auto xx : adj[*it]) {
      if (xx >= y) {
        temp = xx - y;
      } else {
        f = 0;
        break;
      }
      if (temp >= mx) {
        mx = temp;
      }
      if (cur < xx) cur = xx;
    }
    if (!f) break;
    y = cur;
    for (int i = 0; i < mx; i++) p += 'U';
  }
  if (f) {
    cout << "YES"
         << "\n";
    cout << p << "\n";
  } else
    cout << "NO"
         << "\n";
}
int main() {
  ios_base::sync_with_stdio(0);
  int t;
  cin >> t;
  while (t--) {
    solve();
  }
  return 0;
}
