#include <bits/stdc++.h>
using namespace std;
const int N = 2e6 + 5;
long long n, mx = 0, mn = 1e9, ans = 0, k = 1e9;
int one, zero;
bool a[1002][1002];
bool b[1002][1002];
map<char, long long> mp;
int main() {
  int t;
  cin >> t;
  while (t--) {
    int n;
    cin >> n;
    vector<pair<int, int> > v;
    for (int i = 0; i < n; i++) {
      int x, y;
      cin >> x >> y;
      v.push_back({x, y});
    }
    sort(v.begin(), v.end());
    bool q = 0;
    for (int i = 1; i < v.size(); i++) {
      if (v[i].first < v[i - 1].first || v[i].second < v[i - 1].second) q = 1;
    }
    if (q) {
      cout << "NO\n";
      continue;
    }
    pair<int, int> cur = {0, 0};
    string ans = "";
    for (int i = 0; i < v.size(); i++) {
      if (cur.first == v[i].first) {
        for (int j = 0; j < v[i].second - cur.second; j++) {
          ans += 'U';
        }
        cur = v[i];
      } else if (cur.second == v[i].second) {
        for (int j = 0; j < v[i].first - cur.first; j++) {
          ans += 'R';
        }
        cur = v[i];
      } else {
        for (int j = 0; j < v[i].first - cur.first; j++) {
          ans += 'R';
        }
        for (int j = 0; j < v[i].second - cur.second; j++) {
          ans += 'U';
        }
        cur = v[i];
      }
    }
    cout << "YES\n" << ans << "\n";
  }
}
