#include <stdio.h>
#include <string.h>
int maxConsecutiveOnes(char S[], int N, int K) {
    int maxcount = 0, left = 0, zerocount = 0;
    for (int right = 0; right < N; right++) {
        if (S[right] == '0') {
            zerocount++;
        }
        while (zerocount > K) {
            if (S[left] == '0') {
                zerocount--;
            }
            left++;
        }
        int windowsize = right - left + 1;
        if (windowsize > maxcount) {
            maxcount = windowsize;
        }
    }
    return maxcount;
}
void solve() {
    int N, K;
    scanf("%d %d", &N, &K);
    char S[N + 1];
    scanf("%s", S);
    printf("%d\n", maxConsecutiveOnes(S, N, K));
}
int main() {
    int T;
    scanf("%d", &T);
    while (T--) {
        solve();
    }
    return 0;
}