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

int main() {
    int t; cin >> t;
    while (t--) {
        int n; ll k; cin >> n >> k;
        string S; cin >> S;

        vector<int> ones;
        int currentSum = 0;
        for (int i = 0; i < n; i++) {
            if (S[i] == '1') {
                currentSum++;
            } else {
                if (currentSum > 0) {
                    ones.push_back(currentSum);
                    currentSum = 0;
                }
            }
        }
        if (currentSum > 0) {
            ones.push_back(currentSum);
        }

        int windowSum = 0, ans = 0;
        int r = min((int)ones.size(), (int)k+1);
        for (int i = 0; i < r; i++) {
            windowSum += ones[i];
        }
        ans = windowSum;

        for (int i = r; i < (int)ones.size(); i++) {
            windowSum += ones[i] - ones[i - r];
            ans = max(ans, windowSum);
        }

        cout << ans << endl;
    }

    return 0;
}