#define _GLIBCXX_FILESYSTEM
#include<bits/stdc++.h>
using namespace std;
#define ll long long

void solve() {
    int n,k;
    cin >> n >> k;
    string s;
    cin >> s;
    vector<int> v;
    for(int i = 0; i < n; i++) {
        if(s[i] == '1') {
            int now = 0;
            while(i < n and s[i] == '1') {
                i++;
                now++;
            }
            i--;
            v.push_back(now);
        }
    }
    k++;
    k = min(k,(int)v.size());
    int ans = 0,sum = 0;
    for(int i = 0; i < k; i++) {
        sum += v[i];
    }
    ans = sum;
    for(int i = k; i < v.size(); i++) {
        sum += v[i];
        sum -= v[i - k];
        ans = max(ans, sum);
    }
    cout << ans << '\n';
    return;
}

int32_t main() {
    ios_base::sync_with_stdio(false);cin.tie(NULL);
    int tc = 1;
    cin >> tc;
    for(int kase = 1; kase <= tc; kase++) {
        //cout << "Case " << kase << ": ";
        solve();
    }
    return 0;
}