#include<bits/stdc++.h>
using namespace std;

#define int        long long int
#define pb         push_back
#define all(x)     x.begin(),x.end()
#define allr(x)    x.rbegin(),x.rend()
#define ii         pair<int,int>
#define endl       '\n'

void pipra(int tc) {
    int n, k;
    cin >> n >> k;
    string s;
    cin >> s;
    vector<int> a;
    int c = 0;
    for(int i = 0 ; i < n ; i++) {
        if(s[i] == '0') {
            if(c > 0)
                a.pb(c);
            c = 0;
        }
        else
            c++;
    }
    if(c)
        a.pb(c);
    int ans = 0;
    if(k == 0) {
        ans = *max_element(all(a));
    }
    else if(k - 1 >= (int)(a.size())) {
        ans = accumulate(all(a), 0);
    }
    else {
        int ans1 = 0;
        for(int i = 0 ; i <= k ; i++)
            ans1 += a[i];
        ans = max(ans, ans1);
        for(int i = k + 1 ; i < a.size() ; i++) {
            ans1 += a[i];
            ans1 -= a[i - k];
            ans = max(ans, ans1);
        }
    }
    cout << ans << endl;
}

int32_t main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL); cout.tie(NULL);

    int t = 1;
    cin >> t;
    for(int i = 1 ; i <= t ; i++)
        pipra(i);
    return 0;
}