/* 
 *   @author:- MAHMUDUL HASAN SAKIB
 *   DATE & TIME :- 2025-02-14 00:32:20
 *   BANGLADESH , SYLHET.
 */ 
#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <chrono>
#include <cmath>
#include <complex>
#include <deque>
#include <forward_list>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iostream>
#include <limits>
#include <list>
#include <map>
#include <memory>
#include <numeric>
#include <optional>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <tuple>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
using namespace std;
#define fi first
#define se second
#define endl '\n'
#define ll long long
#define ull unsigned long long
#define ld long double
#define PI acos(-1.0)
#define pb push_back
#define mp make_pair
#define vi vector<ll>
#define maxn 500005
#define mod 1000000007
#define inf 1000000007
#define pii pair<ll,ll>
#define vii vector<pii>
#define sz(x) (int)x.size()
#define all(x) x.begin(), x.end()
#define lcm(a,b) ((a*b)/__gcd(a,b));
#define srt(v) sort(v.begin(),v.end())
#define rsrt(v) sort(v.rbegin(),v.rend())
#define setbits(x) __builtin_popcountll(x)
#define rep(i, a, b) for(ll i = (a); i < (b); i++)
#define per(i, a, b) for(int i = (a); i >= (b); i--)
#define rev_str(str) reverse(str.begin(),str.end());
#define print(v) for(auto e:v) cout<<e<<" "; cout<<endl;
#define sum(a) (accumulate((a).begin(), (a).end(), 0LL))
#define printp(v) for(auto e:v) cout<<e.first<<" "<<e.second<<endl;
#define fast ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
bool sortByValue(const pair<int, int>& a, const pair<int, int>& b) {return a.second > b.second;}
const int N = 1e5+10;
const int M = 1e9+7;
bool is_Prime(ll n) {
    if (n < 2) return false; 
    for (ll i = 2; i * i <= n; ++i) {
        if (n % i == 0) return false; 
    }
    return true; 
}
long long Pow(ll a,ll b){
    ll ans = 1;
    while(b>0){
        if(b&1) ans*=a;
        b>>=1;
        a*=a;
    }
    return ans;
}
long long modPow(ll a,ll b){
    ll ans = 1;
    while(b>0){
        if(b&1) ans=(ans*a)%mod;
        b>>=1;
        a=(a*a)%mod;
    }
    return ans;
}
// lies between divisor of a and b == GCD
// prime factorization while the taking the maximum power ==LCM...
int gcd(int a, int b) {
    while (b != 0) {
        int temp = b;
        b = a % b;
        a = temp;
    }
    return a;
}

void solve(){
    ll n,k;cin>>n>>k;
    string s;cin>>s;
    vi p(n),q;
    ll trake = 0;
    ll mx  = 0;
    ll idx = 0;
    rep(i,0,n){
        ll cnt =0;
        if(s[i]=='1'){
            while(s[i]=='1' && i<n){
                cnt++;
                i++;
            }
            trake++;
            if(mx < cnt){
                idx = trake;
                mx = cnt;
            }
            q.push_back(cnt);
            i--;
        }
        else{
            while(s[i]=='0' && i<n){
                i++;
            }
            i--;
        }
    }

    // print(q);
    idx--;
    // cout<<idx<<endl;
    ll left = idx-1;
    ll right = idx+1;
    ll bolo = sz(q);
    while(k>0 && ((left>=0 || right<bolo))){
        k--;
        if(right>=n){
            mx+=q[left];
            left--;
            continue;
        }
        if(left<=0){
            mx+=q[right];
            right++;
            continue;
        }
        if(q[left]>q[right]){
            mx+=q[left];
            left--;
        }
        else if(q[right]>q[left]){
            mx+=q[right];
            right++;
        }
        
    }
    cout<<mx<<endl;
}
void solve2(){
    ll n,k;cin>>n>>k;
    string s;cin>>s;
    vi q,p;
    ll trake = 0;
    ll mx  = 0;
    ll idx = 0;
    rep(i,0,n){
        ll cnt =0;
        if(s[i]=='1'){
            while(s[i]=='1' && i<n){
                cnt++;
                i++;
            }
            trake++;
            if(mx < cnt){
                idx = trake;
                mx = cnt;
            }
            q.push_back(cnt);
            i--;
        }
        else{
            while(s[i]=='0' && i<n){
                i++;
            }
            i--;
        }
    }
    p.push_back(0);
   //print(q);
    
    ll kii=0;
    ll bolo = sz(q);
    rep(i,0,bolo){
        kii+=q[i];
        p.push_back(kii);
    }
    //print(p);
    ll kicchu = 0;
    if(k>=bolo){
        cout<<p.back()<<endl;
    }
    else{
        rep(i,1,bolo+1){
            ll j = i+k;
            if(j<bolo+1){
                ll na = p[j]-p[i-1];
                kicchu = max(na,kicchu);
            }
        }
    }
     cout<<max(kicchu,mx)<<endl;
    // print(q);
}
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    ll t=1;cin>>t;
    while(t--){
        solve2();
    }
    return 0;
}