#include <bits/stdc++.h>
using namespace std;
using LL = long long;
using LD = long double;
LL mod = 1000000007;
bool sumcomp(pair<LL, LL> a, pair<LL, LL> b) {
  if (a.first + a.second == b.first + b.second) {
    return a < b;
  } else {
    return a.first + a.second < b.first + b.second;
  }
}
int main() {
  LL t;
  cin >> t;
  while (t--) {
    LL n;
    cin >> n;
    vector<pair<LL, LL>> p(n);
    for (auto &e : p) {
      cin >> e.first >> e.second;
    }
    sort(p.begin(), p.end(), sumcomp);
    pair<LL, LL> r = {0, 0};
    string move = "";
    bool poss = true;
    for (LL i = 0; i < n; ++i) {
      if (r.first <= p[i].first && r.second <= p[i].second) {
        LL exR = p[i].first - r.first, exU = p[i].second - r.second;
        string R = "R", U = "U";
        while (exR--) {
          move += R;
        }
        while (exU--) {
          move += U;
        }
        r.first = p[i].first;
        ;
        r.second = p[i].second;
      } else {
        poss = false;
        break;
      }
    }
    if (poss) {
      cout << "YES\n";
      cout << move << "\n";
    } else {
      cout << "NO\n";
    }
  }
}
