#include <bits/stdc++.h>
using namespace std;
long long binpow(long long a, long long n, long long mod) {
  long long ans = 1;
  while (n) {
    if (n & 1) ans = (ans * a) % mod;
    a = (a * a) % mod;
    n >>= 1;
  }
  return ans;
}
long long binpow(long long a, long long n) {
  long long ans = 1;
  while (n) {
    if (n & 1) ans *= a;
    a *= a;
    n >>= 1;
  }
  return ans;
}
vector<long long> pr;
void PrDoX(long long x) {
  if (pr.size() > 0) return;
  vector<long long> p(x + 1);
  for (long long i = 2; i <= x; i++) {
    if (p[i] == 0) {
      pr.push_back(i);
      for (long long j = i + i; j <= x; j += i) p[j] = 1;
    }
  }
}
vector<long long> fact(long long x) {
  PrDoX(sqrt(1e9));
  vector<long long> ans;
  long long i = 0, c = sqrt(x), n = pr.size();
  while (x > 1 and pr[i] <= c and i < n) {
    if (x % pr[i] == 0) {
      x /= pr[i];
      ans.push_back(pr[i]);
      c = sqrt(x);
    } else
      i++;
  }
  if (x != 1) ans.push_back(x);
  return ans;
}
int main() {
  long long Q;
  cin >> Q;
  while (Q--) {
    long long n, k;
    cin >> n >> k;
    long long x = 0;
    for (long long i = 0; i < n; i++) {
      cout << char('a' + x);
      x = (x + 1) % k;
    }
    cout << "\n";
  }
  return 0;
}
