#include <bits/stdc++.h>
using namespace std;
int n;
struct Node {
  int x, y;
} node[1005];
bool comp(Node a, Node b) {
  if (a.x < b.x)
    return true;
  else if (a.x == b.x) {
    return a.y < b.y;
  } else
    return false;
}
int main() {
  int T;
  cin >> T;
  while (T--) {
    string s;
    cin >> n;
    for (int i = 1; i <= n; i++) cin >> node[i].x >> node[i].y;
    sort(node + 1, node + 1 + n, comp);
    int tmpx = 0, tmpy = 0, flag = 0;
    for (int i = 1; i <= n; i++) {
      if (i > 1) {
        if (node[i - 1].y > node[i].y) {
          flag = 1;
          break;
        }
      }
      int x = node[i].x - tmpx;
      for (int j = 1; j <= x; j++) s += "R";
      int y = node[i].y - tmpy;
      for (int j = 1; j <= y; j++) s += "U";
      tmpx = node[i].x, tmpy = node[i].y;
    }
    if (flag)
      cout << "NO" << endl;
    else
      cout << "YES" << endl << s << endl;
  }
}
