#include <bits/stdc++.h>
#include<string>
//#include<unordered_set>
     #define ll long long int
    #define fi first
    #define se second
    #define m_p make_pair
    #define endl '\n'
    #define fast_io ios_base::sync_with_stdio(0); cin.tie(0)
    #define endl '\n'
    #define loop(i, a, b) for (long long unsigned int i = a; i < b; i++)
    using namespace std;

   // typedef long long ll;
     typedef pair<ll,ll> pairs;
    const int MAXN = 412345;
    const int MAXINT = 2047483098;
    const ll MOD = 1e9 + 7;
    const int MAX = 1e4;
     const long double pi=2*acosl(0);
    const long double EPS = 1e-10;
     int gcd(int a,int b){if(b==0)return a;return gcd(b,a%b);}

bool isPrime(long long unsigned n){if(n<=1)return false;if(n<=3)return true;
	if(n%2==0||n%3==0)return false;for(int i=5;i*i<=n;i=i+6)
	if(n%i==0||n%(i+2)==0)return false;return true;}

int nCr(int n,int r){int res=1;if(n<r)return -1;r=min(r,n-r);
	loop(i,0,r){res*=(n-i);res/=(i+1);}return res;}

int nPr(int n,int r){int res=1;if(n<r)return -1;
	loop(i,0,r)res*=(n-i);return res;}

ll fact(ll n){
	if(n==1||n==0)
	return 1;
	else
	return (n%MOD)*fact(n-1)%MOD;
}
    void solve() {
    ll n,k;
    cin>>n>>k;
    for(ll i=0;i<k;i++){
    	cout<<"a";
	}
	ll p=0;
	for(ll i=0;i<n-k;i++){
		char c='b'+p;
		cout<<c;
		p++;
		if(p>1)
		p=-1;
		
	}
	cout<<endl;
}

    int main()
    {
        fast_io;

        int T;
      cin >> T;
     // T=1;
        while(T--) {
            solve();
        }

        return 0;
}



