#include <bits/stdc++.h>
using namespace std;
int main() {
  int t;
  cin >> t;
  for (int ask = 0; ask < t; ask++) {
    int arr[1001][1001];
    for (int z = 0; z < 1001; z++) {
      for (int g = 0; g < 1001; g++) {
        arr[z][g] = 0;
      }
    }
    int n;
    cin >> n;
    int a, b;
    for (int k = 0; k < n; k++) {
      cin >> a >> b;
      arr[a][b] = 1;
    }
    string hum = "";
    int q = 0;
    int w = 0;
    int luli = 0;
    for (int k = 0; k <= 1000; k++) {
      for (int as = 0; as <= 1000; as++) {
        if (arr[k][as] == 1 && as >= q) {
          int lul = as - q;
          int kul = k - w;
          hum.append(kul, 'R');
          hum.append(lul, 'U');
          q = as;
          w = k;
          luli++;
        }
      }
    }
    if (luli == n) {
      cout << "YES" << endl;
      cout << hum << endl;
    } else {
      cout << "NO" << endl;
    }
  }
}
