#include<bits/stdc++.h>
using namespace std;
#define ll long long int 
int main()
{
  ll tc;
    cin>>tc;
    while(tc--)
    {
        ll n,k;
        cin>>n>>k;
        string s;
        cin>>s;
        ll c=0;
        vector<ll>v;
        for(int i=0;i<s.size();i++)
        {
            if(s[i]=='1')
                c++;
            else if(s[i]=='0' && c>0)
            {
                v.push_back(c);
                c=0;
            }
           if(s[i]=='0')
                c=0;
        }
        if(c>0)
            v.push_back(c);
     
        ll l=0,r=0,mx=0,sum=0;
        while(r<v.size())
        {
           sum+=v[r];
            if((r-l)+1<=k+1)
            {
                mx=max(mx,sum);
                
              
                
            }
           else 
           {
               sum-=v[l];
               l++;
               mx=max(mx,sum);
           }
            r++;
        }
        cout<<mx<<endl;
    }
}