#include <bits/stdc++.h>
using namespace std;
struct node {
  int x;
  int y;
};
int main() {
  int t, n;
  cin >> t;
  for (int j = 0; j < t; j++) {
    cin >> n;
    vector<node> arr(n);
    int x, y;
    vector<char> s;
    for (int i = 0; i < n; i++) {
      cin >> x >> y;
      arr[i].x = x;
      arr[i].y = y;
    }
    for (int i = 0; i < n - 1; i++) {
      for (int j = i + 1; j < n; j++) {
        if (arr[j].x == arr[i].x) {
          if (arr[j].y < arr[i].y) swap(arr[i], arr[j]);
          continue;
        }
        if (arr[j].x < arr[i].x) {
          swap(arr[i], arr[j]);
        }
      }
    }
    int x1 = 0;
    int y1 = 0;
    int i;
    for (i = 0; i < n; i++) {
      int a = x1;
      int b = y1;
      if (arr[i].x >= x1 && arr[i].y >= y1) {
        x1 = arr[i].x;
        y1 = arr[i].y;
        if (a != x1)
          for (int i = a; i < x1; i++) s.push_back('R');
        if (b != y1)
          for (int i = b; i < y1; i++) s.push_back('U');
      } else {
        cout << "NO" << endl;
        break;
      }
    }
    if (i == n) {
      cout << "YES" << endl;
      for (int i = 0; i < s.size(); i++) cout << s[i];
      cout << endl;
    }
  }
  return 0;
}
