#include <bits/stdc++.h>
using namespace std;
long long max1 = (long long)1e9;
struct cord {
  int x, y;
};
bool compare(struct cord c, struct cord b) {
  if (c.y < b.y)
    return 1;
  else if (c.y == b.y) {
    if (c.x < b.x)
      return 1;
    else
      return 0;
  } else
    return 0;
}
int main() {
  long long i, j, k, n, m, ct = 0, t, ans = 0, flag = 0, x1, y1;
  cin >> t;
  while (t--) {
    cin >> n;
    flag = 0;
    struct cord *a = (struct cord *)malloc(sizeof(struct cord) * n);
    for (i = 0; i < n; i++) {
      cin >> x1 >> y1;
      a[i].x = x1;
      a[i].y = y1;
    }
    sort(a, a + n, compare);
    x1 = 0;
    y1 = 0;
    vector<char> str;
    for (i = 0; i < n; i++) {
      if (y1 <= a[i].y && flag == 0) {
        if (x1 <= a[i].x && flag == 0) {
          while (x1 != a[i].x && flag == 0) {
            str.push_back('R');
            x1++;
          }
        } else if (x1 > a[i].x) {
          flag = 1;
          break;
        }
        while (y1 != a[i].y) {
          str.push_back('U');
          y1++;
        }
      }
    }
    if (flag == 0) {
      cout << "YES\n";
      for (char ch : str) cout << ch;
    } else
      cout << "NO";
    cout << endl;
  }
  return 0;
}
