ProblemB

import java.io.*;
import java.util.*;

public class Problem1
{

    public static void main(String args[]) throws IOException
    {
        Scanner sc = new Scanner(System.in);
        int t = sc.nextInt();
        for (int i = 0; i<t ; i++)
        {
            int n = sc.nextInt();
            int k = sc.nextInt();
            StringBuilder sb=new StringBuilder("");
            for (int x = 0; x<n-2; x++)
            sb.append("a");
            sb.append("bb");
            System.out.println(sb);
            int length = sb.length();
            int b1 = length -2;
            int b2 = length -1;
            int iter = 1;
            while (b1 >0 || b2 >1 )
            {
                if (iter == k)
                {
                    System.out.println(sb);
                    break;
                }
                if (b1-b2 >1)
                {
                    sb.replace(b2,b2+1,"a");
                    sb.replace(b2-1,b2, "b");
                    b2--;
                }
                else
                {
                    sb.replace(b1,b1+1,"a");
                    sb.replace(b1-1,b1, "b");
                    b1--;
                }
                iter ++;
            }
        }
    }
}


class Scanner
{
    StringTokenizer st;
    BufferedReader br;

    public Scanner(InputStream s)
    {
        br = new BufferedReader(new InputStreamReader(s));
    }

    public String next() throws IOException
    {
        while (st == null || !st.hasMoreTokens())
            st = new StringTokenizer(br.readLine());
        return st.nextToken();
    }

    public int nextInt() throws IOException
    {
        return Integer.parseInt(next());
    }

    public long nextLong() throws IOException
    {
        return Long.parseLong(next());
    }

    public String nextLine() throws IOException
    {
        return br.readLine();
    }

    public double nextDouble() throws IOException
    {
        String x = next();
        StringBuilder sb = new StringBuilder("0");
        double res = 0, f = 1;
        boolean dec = false, neg = false;
        int start = 0;
        if (x.charAt(0) == '-')
        {
            neg = true;
            start++;
        }
        for (int i = start; i < x.length(); i++)
            if (x.charAt(i) == '.')
            {
                res = Long.parseLong(sb.toString());
                sb = new StringBuilder("0");
                dec = true;
            } else
            {
                sb.append(x.charAt(i));
                if (dec)
                    f *= 10;
            }
        res += Long.parseLong(sb.toString()) / f;
        return res * (neg ? -1 : 1);
    }

    public boolean ready() throws IOException
    {
        return br.ready();
    }


}