#include <bits/stdc++.h>
#define pb push_back
#define pi 2*acos(0.0)
#define f first
#define s second
#define inf INT_MAX
#define MXN 500001
#define endl "\n"
#define eps 1e-6
#define mod 1000000007
#define all(x) x.begin(), x.end()
#define rev(x) x.rbegin(), x.rend()
#define spc(x) cout << fixed << setprecision(x)
#define fastio {ios_base::sync_with_stdio(false); cin.tie(NULL);}

typedef long long ll;
using namespace std;

void solve() {
    ll n, k;
    cin >> n >> k;

    string s; 
    cin >> s;

    vector<ll> v;
    ll cnt = 0;

    for (int i = 0; i < s.size(); i++) {
        if (s[i] == '1') {
            cnt++;
        } else {
            if (cnt > 0) {
                v.pb(cnt);
            }
            cnt = 0;
        }
    }
    if (cnt > 0) {
        v.pb(cnt);  
    }

    if (v.empty()) {
        cout << 0 << endl;
        return;
    }

    ll left = 0, right = 0, sum = 0, mx = 0;

    while (right < v.size()) {
        sum += v[right];

        while (right - left + 1 > k + 1) {
            sum -= v[left];
            left++;
        }

        mx = max(mx, sum);
        right++;
    }

    cout << mx << endl;
}

int32_t main() {
    fastio
    int t;
    cin >> t;
    while (t--) {
        solve();
    }
    return 0;
}