#include<stdio.h>
int main()
{
int i,j,n,a[50],b[50],k,l,m;
scanf("%d",&n);
for(i=0;i<n;i++)
{scanf("%d%d",&a[i],&b[i]);
}
for(i=0;i<n;i++)
{for(j=1;j<b[i]*a[i];j++)
{for(k=1;k<=a[i];k++)
{if(j%a[i]==0&&j!=b[i]*a[i])j++;
l=j%a[i];
if(k==l||k==a[i]-l+1)
{printf("X");
}
else printf(" ");
}printf("\n");
}if(j==b[i]*a[i])
{for(m=1;m<=a[i];m++)
{if(m==1||m==a[i])printf("X");
else printf(" ");
}printf("\n");
}printf("\n");
}
return 0;
}