#include <bits/stdc++.h>
using namespace std;
struct info {
  int x, y;
};
bool cmp(struct info a, struct info b) {
  if (a.x == b.x) return a.y < b.y;
  return a.x < b.x;
}
int main() {
  int t;
  cin >> t;
  while (t--) {
    int n;
    cin >> n;
    struct info a[n + 2];
    for (int i = 0; i < n; i++) cin >> a[i].x >> a[i].y;
    sort(a, a + n, cmp);
    int ct = 0;
    string s;
    s.clear();
    int px = 0, py = 0;
    bool f = 1;
    for (int i = 0; i < n; i++) {
      if (a[i].x >= px) {
        for (int j = 0; j < (a[i].x - px); j++) s += 'R';
        px = a[i].x;
      } else {
        f = 0;
        break;
      }
      if (a[i].y >= py) {
        for (int j = 0; j < (a[i].y - py); j++) s += 'U';
        py = a[i].y;
      } else {
        f = 0;
        break;
      }
    }
    if (!f)
      cout << "NO" << endl;
    else {
      cout << "YES" << endl;
      cout << s << endl;
    }
  }
  return 0;
}
