#include <bits/stdc++.h>
#include <cmath>
#include <bitset>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef tree<int, null_type, less_equal<int>, rb_tree_tag, tree_order_statistics_node_update> pbds;
#define ll long long int
#define lld long double
#define yes cout << "Yes" << endl
#define no cout << "No" << endl
#define gcd(a, b) __gcd(a, b)
#define lcm(a, b) ((a * b) / gcd(a, b))
#define pi acos(-1.00)
ll rec(vector<vector<ll>>&a,vector<ll>&v,ll in,ll jn,ll n,ll m){
  if(in==n-1&& a[in][jn]==2){
      return jn;
  }
  if(a[in][jn]==1){
    a[in][jn]=2;
      ll x=rec(a,v,in,jn+1,n,m);
      
      return x;
  }
  if(a[in][jn]==3){
    a[in][jn]=2;
    ll x=rec(a,v,in,jn-1,n,m);
   
    return x;
}
   return rec(a,v,in+1,jn,n,m);
}
void evan(int t)
{
  ll n;cin>>n;
  ll k;cin>>k;
  string s;
  cin>>s;
  vector<ll>v;
  ll cnt=0;
  for(int i=0;i<n;i++){
     if(s[i]=='1'){
      cnt++;
     }
     else{
      if(cnt!=0)v.push_back(cnt);
      cnt=0;
     }
  }
  if(cnt!=0)v.push_back(cnt);
  ll maxx=-1;
  deque<ll>q;
  ll temp=0;
  n=v.size();
  
  for(int i=0;i<=min(k,n-1);i++){
       q.push_back(v[i]);
        temp+=v[i];
  }
  if(k+1>=n){
    cout<<temp<<"\n";return;
  }
  maxx=temp;
 
  for(int i=q.size();i<n;i++){
      temp-=q.front();
      q.pop_front();
      q.push_back(v[i]);
      temp+=v[i];
      maxx=max(temp,maxx);
  }
  cout<<maxx<<"\n";

}
signed main()
{
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(nullptr);
  int t = 1;
  cin >> t;
  for (int i = 1; i <= t; i++)
  {
    evan(i);
  }
}