#include <bits/stdc++.h>
using namespace std;
struct P {
  int x, y;
  bool operator<(const P& rhp) const {
    return x < rhp.x || (x == rhp.x && y < rhp.y);
  }
} G[1005];
int main() {
  int T, N;
  scanf("%d", &T);
  while (T--) {
    char move[2005];
    int len = 0;
    int px = 0, py = 0;
    scanf("%d", &N);
    for (int i = 0; i < N; i++) {
      scanf("%d%d", &G[i].x, &G[i].y);
    }
    sort(G, G + N);
    bool flag = true;
    for (int i = 0; i < N; i++) {
      if (G[i].x < px || G[i].y < py) {
        flag = false;
        break;
      }
      int dx = G[i].x - px, dy = G[i].y - py;
      px = G[i].x, py = G[i].y;
      for (int j = 0; j < dx; j++) move[len++] = 'R';
      for (int j = 0; j < dy; j++) move[len++] = 'U';
    }
    if (!flag)
      printf("NO\n");
    else {
      move[len] = '\0';
      printf("YES\n%s\n", move);
    }
  }
  return 0;
}
