#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e3 + 5;
int t, n, x[maxn], y[maxn], num, xr, yr;
bool b;
int main() {
  cin >> t;
  for (int i = 0; i < t; i++) {
    cin >> n;
    for (int j = 0; j < n; j++) {
      cin >> x[j] >> y[j];
      if (b == 0) {
        for (int o = 0; o < j; o++) {
          if (x[o] > x[j]) {
            swap(x[j], x[o]);
            swap(y[j], y[o]);
          }
          if (x[o] == x[j] && y[o] > y[j]) {
            swap(y[o], y[j]);
          }
        }
      }
      if (j > 0 && b == 0) {
        for (int o = 1; o <= j; o++) {
          if (y[o] < y[o - 1]) {
            b = 1;
            break;
          }
        }
      }
    }
    if (b == 0) {
      xr = 0;
      yr = 0;
      cout << "YES" << endl;
      for (int j = 0; j < n; j++) {
        while (xr < x[j]) {
          cout << "R";
          xr++;
        }
        while (yr < y[j]) {
          cout << "U";
          yr++;
        }
      }
      cout << endl;
    } else {
      cout << "NO" << endl;
    }
    b = 0;
  }
}
