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

int main() {
    ios::sync_with_stdio(0);
    cin.tie(NULL), cout.tie(NULL);
    
    int t;
    cin >> t;
    
    while (t--)
    {
        int n, k;
        string s;
        cin >> n >> k >> s;
        
        k++;
        vector<int> X;
        
        for (int i = 0; i < n; i++)
        {
            if (s[i] == '0')
                continue;
            
            int ptr = i;
            
            while (s[ptr] == '1')
                ptr++;
            
            X.push_back(ptr - i);
            i = ptr - 1;
        }
        
        int curr = 0;
        k = min(k, (int) X.size());
        
        for (int i = 0; i < k; i++)
            curr += X[i];
        
        int res = curr;
        
        for (int i = k; i < X.size(); i++)
        {
            curr += X[i] - X[i - k];
            res = max(res, curr);
        }
        
        cout << res << "\n";
    }
    
    return 0;
}