#include <bits/stdc++.h>
using namespace std;
const int N = 1e3 + 5;
struct node {
  int x, y;
};
node a[N];
bool cmp(node a, node b) {
  if (a.x != b.x) return a.x < b.x;
  return a.y < b.y;
}
vector<char> ans;
int main() {
  int t;
  scanf("%d", &t);
  while (t--) {
    int n;
    scanf("%d", &n);
    for (int i = 1; i <= n; i++) {
      scanf("%d%d", &a[i].x, &a[i].y);
    }
    sort(a + 1, a + n + 1, cmp);
    int x = 0, y = 0;
    int flag = 0;
    for (int i = 1; i <= n; i++) {
      if (x <= a[i].x) {
        for (; x < a[i].x; x++) {
          ans.push_back('R');
        }
      } else if (x > a[i].x) {
        flag = 1;
        break;
      }
      if (y <= a[i].y) {
        for (; y < a[i].y; y++) {
          ans.push_back('U');
        }
      } else if (y > a[i].y) {
        flag = 1;
        break;
      }
    }
    if (flag) {
      printf("NO\n");
    } else {
      printf("YES\n");
      for (int i = 0; i < ans.size(); i++) {
        printf("%c", ans[i]);
      }
      printf("\n");
    }
    ans.clear();
  }
}
