#include <stdio.h>

int maxConsecutiveOnes(int N, int K, const char* S) {
    int left = 0, right = 0, max_len = 0, count_zeros = 0;

    while (right < N) {
      
        if (S[right] == '0') {
            count_zeros++;
        }

       
        while (count_zeros > K) {
            if (S[left] == '0') {
                count_zeros--;
            }
            left++;
        }

        
        max_len = (right - left + 1) > max_len ? (right - left + 1) : max_len;

        right++;
    }

    return max_len;
}

int main() {
    int T;
    scanf("%d", &T);

    while (T--) {
        int N, K;
        scanf("%d %d", &N, &K);
        
        char S[N + 1];  
        scanf("%s", S);

        int result = maxConsecutiveOnes(N, K, S);

        printf("%d\n", result);
    }

    return 0;
}