#include <bits/stdc++.h>
int main() {
  int t;
  scanf("%d", &t);
  while (t--) {
    int n;
    scanf("%d", &n);
    int ar[n + 1][2];
    ar[0][0] = 0;
    ar[0][1] = 0;
    for (int i = 1; i <= n; i++) scanf("%d%d", &ar[i][0], &ar[i][1]);
    for (int i = 1; i <= n; i++) {
      for (int j = 1; j <= n - 1; j++) {
        if (ar[j + 1][0] < ar[j][0]) {
          int t = ar[j + 1][0];
          ar[j + 1][0] = ar[j][0];
          ar[j][0] = t;
          int tt = ar[j + 1][1];
          ar[j + 1][1] = ar[j][1];
          ar[j][1] = tt;
        }
      }
    }
    for (int i = 1; i <= n; i++) {
      for (int j = 1; j <= n - 1; j++) {
        if (ar[j + 1][1] < ar[j][1] && ar[j + 1][0] == ar[j][0]) {
          int t = ar[j + 1][1];
          ar[j + 1][1] = ar[j][1];
          ar[j][1] = t;
        }
      }
    }
    int f = 0;
    for (int i = 0; i < n; i++) {
      if (ar[i][0] > ar[i + 1][0] || ar[i][1] > ar[i + 1][1]) {
        f = 1;
        break;
      }
    }
    if (f == 1)
      printf("NO\n");
    else {
      printf("YES\n");
      for (int i = 0; i < n; i++) {
        int cnt = ar[i + 1][0] - ar[i][0];
        while (cnt--) printf("R");
        int ccnt = ar[i + 1][1] - ar[i][1];
        while (ccnt--) printf("U");
      }
      printf("\n");
    }
  }
  return 0;
}
