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

#define		Alhamdulillah 		ios_base::sync_with_stdio(0); cin.tie(0);
#define	    ll 			 		long long
#define	    ld 			 		long double
#define	    ull 			 	unsigned long long
#define	    lcm(a,b) 			((a*b)/__gcd(a,b))
#define	    endl 			 	"\n"
#define	    pb 					push_back
#define	    ppb 				pop_back
#define	    all(c) 				c.begin(),c.end()
#define     srt(v)             	sort(v.begin(),v.end())
#define	    rsrt(v)            	sort(v.rbegin(),v.rend())
#define     printp(p)          	for(auto i:p)   cout << i.first <<  " " << i.second << endl; cout << endl;
#define     printv(v)          	for(auto i:v)   cout << i <<  " "; cout << endl;
#define     printm(m)          	for(auto [x,y]:m)   cout << x <<  " " << y << endl; cout << endl;


void solve(){
    string s;
    int n, k, ct = 0, cur = 0, mx = 0;  cin >> n >> k >> s;
    for(int i=0;i<n;i++){
        if(s[i] == '1') ct++, cur++;
        else{
            mx = max(mx,cur);
            cur = 0;  
        }
    }
    mx = max(mx,cur);    
    int rem = ct - mx;
    cout << mx + min(k,rem) << endl;
}


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