#include <bits/stdc++.h>

using namespace std;
using ll = long long;
const ll mod = 1e9 + 7;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    ll testcases;
    cin >> testcases;
    while (testcases--) {
        
        ll n , k;
        cin >> n >> k;
        
        string s;
        cin >> s;
        
        char num = s[0];
        ll i = 0 , cnt = 0;
        vector<ll> arr;
        while(i < n){
            if(s[i] == num){
                cnt++;
            }
            else{
                if(cnt && num == '1') arr.push_back(cnt);
                num = s[i];
                cnt = 0;
                continue;
            }
            i++;
        }
        
        if(cnt && num == '1') arr.push_back(cnt);
        
        k++;
        if(k >= arr.size()){
            ll ans = 0;
            for(auto p : arr) ans += p;
            cout << ans << "\n";
            continue;
        }
        
        ll ans = 0 , curr = 0;
        for(ll i = 0 ; i < arr.size() ; i++){
            curr += arr[i];
            if(i - k >= 0) curr -= arr[i - k];
            ans = max(ans , curr);
        }
        
        cout << ans << "\n";
        
        
    }
    return 0;
}
// Author : Raj (raj_singh35)