#include <bits/stdc++.h>
using namespace std;
string make(int a, char c) {
  if (a > 0) {
    string s2(a, c);
    return s2;
  } else {
    string s2 = "";
    return s2;
  }
}
bool boolean(pair<int, int> p1, pair<int, int> p2) {
  if (p1.first > p2.first) {
    return false;
  } else if (p1.first < p2.first)
    return true;
  else {
    if (p1.second > p2.second)
      return false;
    else
      return true;
  }
}
int main() {
  int t;
  cin >> t;
  while (t--) {
    int n, a, b, i;
    cin >> n;
    vector<pair<int, int> > vect;
    for (i = 0; i < n; i++) {
      cin >> a >> b;
      vect.push_back(make_pair(a, b));
    }
    sort(vect.begin(), vect.end(), boolean);
    pair<int, int> temp;
    temp = vect[0];
    string s1 = "" + make(temp.first, 'R') + make(temp.second, 'U');
    i = 1;
    for (i = 1; i < n; i++) {
      if (((vect[i].first) - (temp.first)) < 0 ||
          ((vect[i].second) - (temp.second)) < 0) {
        cout << "NO" << endl;
        break;
      } else {
        s1 = s1 + make((vect[i].first) - (temp.first), 'R') +
             make((vect[i].second) - (temp.second), 'U');
        temp = vect[i];
      }
    }
    if (i == n) cout << "YES" << endl << s1 << endl;
  }
  return 0;
}
