#include <bits/stdc++.h>
using namespace std;
vector<int> x, y;
int main() {
  int testCases;
  cin >> testCases;
  for (int i = 0; i < testCases; i++) {
    x.clear();
    y.clear();
    int n;
    cin >> n;
    for (int j = 0; j < n; j++) {
      int xx, yy;
      cin >> xx >> yy;
      x.push_back(xx);
      y.push_back(yy);
    }
    bool good = true;
    for (int j = 0; j < x.size() && good == true; j++) {
      for (int k = j + 1; k < x.size(); k++) {
        if (x[j] < x[k]) {
          if (y[j] > y[k]) {
            cout << "NO" << endl;
            good = false;
            break;
          }
        } else if (x[j] > x[k]) {
          if (y[j] < y[k]) {
            cout << "NO" << endl;
            good = false;
            break;
          }
        }
      }
    }
    if (good) {
      cout << "YES" << endl;
      sort(x.begin(), x.end());
      sort(y.begin(), y.end());
      int cX = 0;
      int cY = 0;
      for (int j = 0; j < x.size(); j++) {
        for (int k = 0; k < (x[j] - cX); k++) {
          cout << "R";
        }
        cX = x[j];
        for (int k = 0; k < (y[j] - cY); k++) {
          cout << "U";
        }
        cY = y[j];
      }
      cout << endl;
    }
  }
}
