#include <bits/stdc++.h>
using namespace std;
long long int gcd(long long int a, long long int b) {
  if (a == 0) return b;
  return gcd(b % a, a);
}
long long int modulo(long long int a, long long int b) {
  long long int r = a % b;
  return r < 0 ? r + b : r;
}
long long int longrem(string k, long long int n) {
  int now = 0;
  for (int i = 0; i < k.size(); i++) {
    now = (now * 10) % n;
    now = (now + k[i] - '0') % n;
  }
  return now;
}
long long int ncr(long long int n, long long int k) {
  long long int res = 1;
  if (k > n - k) k = n - k;
  for (long long int i = 0; i < k; ++i) {
    res *= (n - i);
    res /= (i + 1);
  }
  return res;
}
long long int binaryToDecimal(long long int n) {
  long long int num = n;
  long long int dec_value = 0;
  long long int base = 1;
  long long int temp = num;
  while (temp) {
    long long int last_digit = temp % 10;
    temp = temp / 10;
    dec_value += last_digit * base;
    base = base * 2;
  }
  return dec_value;
}
void decToBinary(int n) {
  int binaryNum[32];
  int i = 0;
  while (n > 0) {
    binaryNum[i] = n % 2;
    n = n / 2;
    i++;
  }
  for (int j = i - 1; j >= 0; j--) cout << binaryNum[j];
}
long long int prime(long long int n) {
  long long int flag = 0;
  if (n == 1 || n == 2) {
    flag = 0;
  } else {
    if (n % 2 == 0)
      flag = 1;
    else {
      long long int i = 3;
      while (i <= sqrt(n) && flag == 0) {
        if (n % i == 0) flag = 1;
        i = i + 3;
      }
    }
  }
  return flag;
}
long long int ispal(string str, string s) {
  long long int flag = 0;
  reverse(str.begin(), str.end());
  if (str == s) {
    flag = 1;
  }
  return flag;
}
long long int ispalself(string str) {
  long long int flag = 0;
  string s = str;
  reverse(str.begin(), str.end());
  if (str == s) {
    flag = 1;
  }
  return flag;
}
struct pt {
  long long int x;
  long long int y;
};
long long int fun(struct pt a, struct pt b) {
  long long int ret = 1;
  if (a.x > b.x) {
    ret = 0;
  } else if (a.x == b.x) {
    if (a.y > b.y) {
      ret = 0;
    }
  }
  return ret;
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long int t;
  cin >> t;
  while (t--) {
    long long int n, tm, i;
    cin >> n;
    struct pt a[n];
    for (i = 0; i < n; i++) {
      cin >> a[i].x >> a[i].y;
    }
    sort(a, a + n, fun);
    long long int x = 0, y = 0, flag = 1;
    i = 0;
    string str = "";
    while (flag && i < n) {
      if (a[i].x < x || a[i].y < y) {
        flag = 0;
      } else {
        if (a[i].x > x) {
          str += "R";
          x++;
        } else if (a[i].y > y) {
          str += "U";
          y++;
        }
      }
      if (a[i].x == x && a[i].y == y) {
        i++;
      }
    }
    if (flag) {
      cout << "YES\n";
      cout << str << "\n";
    } else {
      cout << "NO\n";
    }
  }
}
