#include<bits/stdc++.h>
using namespace std;

void in(int a[], int n) {
  for(int i = 1; i <= n; i++) {
    cout << char('A'+a[i]-1);
  }
  cout << '\n';
}

int main() {
  int t; cin >> t;
  while(t--) {
    int n, k; cin >> n >> k;
    int a[k+1];
    for(int i = 1; i <= k; i++) {
      a[i] = i;
    }
    int ok = 1;
    while(ok) {
      in(a, k);
      int i = k;
      while(i >= 1 && a[i] == n-k+i) {
        i--;
      }
      if(i == 0) ok = 0;
      else {
        a[i]++;
        for(int j = i+1; j <= k; j++) a[j] = a[i]+j-i;
      }
    }
    cout << endl;
  }
}