#include <bits/stdc++.h>
using namespace std;
inline int read() {
  char c = getchar();
  int x = 0, f = 1;
  for (; !isdigit(c); c = getchar())
    if (c == '-') f = -1;
  for (; isdigit(c); c = getchar()) x = x * 10 + c - '0';
  return x * f;
}
struct Node {
  int x, y;
} a[1005];
inline void solve() {
  int N = read();
  for (int i = 1; i <= N; i++) {
    a[i].x = read();
    a[i].y = read();
  }
  a[0] = {0, 0};
  sort(a + 1, a + N + 1, [&](Node a, Node b) {
    if (a.x != b.x) return a.x < b.x;
    return a.y < b.y;
  });
  bool flg = true;
  for (int i = 1; i < N; i++)
    if (a[i].y > a[i + 1].y) {
      flg = false;
      break;
    }
  if (!flg)
    puts("NO");
  else {
    puts("YES");
    for (int i = 0; i < N; i++) {
      for (int j = a[i].x + 1; j <= a[i + 1].x; j++) putchar('R');
      for (int j = a[i].y + 1; j <= a[i + 1].y; j++) putchar('U');
    }
    puts("");
  }
}
int main() {
  int T = read();
  while (T--) solve();
  return 0;
}
