#include <bits/stdc++.h>
using namespace std;
using ll = long long int;
const ll mod = 1000000007;
const ll M = 1000000000000000000ll;
inline ll add(ll a, ll b) { return ((a % mod + b % mod) % mod); }
inline ll sub(ll a, ll b) { return ((a % mod - b % mod + mod) % mod); }
inline ll mult(ll a, ll b) { return (((a % mod) * (b % mod)) % mod); }
inline ll power(ll n, ll x) {
  ll p = 1;
  while (x != 0) {
    if (x % 2 == 0) {
      n = mult(n, n);
      x = x / 2;
    }
    p = mult(p, n);
    x--;
  }
  return p;
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  ll t;
  cin >> t;
  while (t--) {
    ll n;
    cin >> n;
    vector<pair<ll, ll>> v;
    for (ll i = 0; i < n; i++) {
      ll x, y;
      cin >> x >> y;
      v.push_back({x, y});
    }
    sort(v.begin(), v.end());
    string s = "";
    ll up = 0, right = 0, fl = 0;
    for (ll i = 0; i < v.size(); i++) {
      ll px, py;
      px = v[i].first;
      py = v[i].second;
      if (px < right || py < up) {
        fl = 1;
        break;
      } else {
        ll dx, dy;
        dx = px - right;
        dy = py - up;
        while (dx != 0) {
          s = s + 'R';
          dx--;
        }
        while (dy != 0) {
          s = s + 'U';
          dy--;
        }
        up = py;
        right = px;
      }
    }
    if (fl == 1)
      cout << "NO\n";
    else {
      cout << "YES\n";
      cout << s << "\n";
    }
  }
}
