#include <bits/stdc++.h>
using namespace std;
long long int po(long long int x, long long int n) {
  if (n == 0)
    return 1;
  else if (n % 2 == 0)
    return po((x * x) % 1000000007, n / 2);
  else
    return (x * po((x * x) % 1000000007, (n - 1) / 2)) % 1000000007;
}
long long int GCD(long long int A, long long int B) {
  if (B == 0)
    return A;
  else
    return GCD(B, A % B);
}
void fu(string& s, char a, long long int x) {
  for (int i = 0; i < x; ++i) s.push_back(a);
}
int main() {
  ios_base::sync_with_stdio(false), cin.tie(NULL), cout.tie(NULL);
  long long int t = 1;
  cin >> t;
  while (t--) {
    long long int n;
    cin >> n;
    vector<pair<long long int, long long int>> a(n);
    for (int i = 0; i < n; ++i) cin >> a[i].first >> a[i].second;
    sort(a.begin(), a.end());
    long long int x = 0, y = 0;
    string ans = "";
    long long int f = 0;
    for (int i = 0; i < a.size(); ++i) {
      long long int ax = a[i].second, ay = a[i].first;
      if (ax < x || ay < y) {
        f = 1;
        break;
      }
      fu(ans, 'R', ay - y);
      fu(ans, 'U', ax - x);
      y = ay;
      x = ax;
    }
    if (f)
      cout << "NO\n";
    else
      cout << "YES\n" << ans << "\n";
  }
}
