#include <bits/stdc++.h>
using namespace std;
bool comp(const pair<int, int> &p1, const pair<int, int> &p2) {
  if (p1.first < p2.first) {
    return true;
  } else if (p1.first > p2.first) {
    return false;
  } else {
    return p1.second < p2.second;
  }
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int t;
  cin >> t;
  while (t--) {
    int n;
    cin >> n;
    vector<pair<int, int> > data(n);
    for (int i = 0; i < n; ++i) {
      cin >> data[i].first >> data[i].second;
    }
    sort(data.begin(), data.end(), comp);
    string ans = "";
    int curx = 0;
    int cury = 0;
    bool flag = false;
    for (auto p : data) {
      if (p.first < curx) {
        flag = true;
        break;
      }
      if (p.second < cury) {
        flag = true;
        break;
      }
      while (curx < p.first) {
        ans += "R";
        ++curx;
      }
      while (cury < p.second) {
        ans += "U";
        ++cury;
      }
    }
    if (!flag) {
      cout << "YES\n";
      cout << ans << "\n";
    } else {
      cout << "NO\n";
    }
  }
  return 0;
}
