#include <bits/stdc++.h>
using namespace std;
const int manx = 2e4 + 10;
char path[4000];
struct node {
  int x, y;
} point[1010];
bool cmp(node a, node b) {
  if (a.x == b.x) return a.y < b.y;
  return a.x < b.x;
}
int main() {
  int t, n, x, y, cou;
  scanf("%d", &t);
  while (t--) {
    cou = 0;
    scanf("%d", &n);
    for (int i = 0; i < n; i++) {
      scanf("%d%d", &x, &y);
      point[i].x = x, point[i].y = y;
    }
    point[n].x = 0, point[n].y = 0;
    sort(point, point + n + 1, cmp);
    int flag = 1;
    for (int i = 0; i <= n - 1; i++) {
      int l, h;
      if (point[i].x <= point[i + 1].x && point[i].y <= point[i + 1].y)
        l = point[i + 1].x - point[i].x, h = point[i + 1].y - point[i].y;
      else {
        flag = 0;
        break;
      }
      for (int i = 0; i < l; i++) path[cou++] = 'R';
      for (int i = 0; i < h; i++) path[cou++] = 'U';
    }
    path[cou] = '\0';
    if (flag)
      printf("YES\n%s\n", path);
    else
      printf("NO\n");
  }
  return 0;
}
