#include <bits/stdc++.h>
using namespace std;
struct node {
  int x, y;
} pos[1020];
char a[100010];
bool cmp(node a, node b);
int main() {
  int q, n;
  cin >> q;
  while (q--) {
    int cur = 0;
    bool status = 0;
    cin >> n;
    for (int i = 0; i < n; i++) cin >> pos[i].x >> pos[i].y;
    sort(pos, pos + n, cmp);
    int x = 0, y = 0;
    for (int i = 0; i < n; i++) {
      int ax = pos[i].x - x;
      int ay = pos[i].y - y;
      if (ax > 0)
        for (int j = 0; j < ax; j++) a[cur++] = 'R';
      if (ay > 0)
        for (int j = 0; j < ay; j++) a[cur++] = 'U';
      if (ax < 0 || ay < 0) {
        status = 1;
        break;
      }
      x = pos[i].x;
      y = pos[i].y;
    }
    if (!status) {
      cout << "YES" << endl;
      for (int i = 0; i < cur; i++) cout << a[i];
      cout << endl;
    } else
      cout << "NO" << endl;
  }
}
bool cmp(node a, node b) {
  if (a.x == b.x) return a.y < b.y;
  return a.x < b.x;
}
