#include <bits/stdc++.h>
using namespace std;
int main() {
  int t;
  cin >> t;
  while (t--) {
    int n;
    cin >> n;
    string s;
    cin >> s;
    string p = "";
    if (s[0] == '0') {
      for (int i = 0; i < n / 2; i++) {
        p += '0';
        p += '1';
      }
    } else {
      for (int i = 0; i < n / 2; i++) {
        p += '1';
        p += '0';
      }
    }
    int cnt = 0;
    for (int i = 0; i < n; i++) {
      if (s[i] != p[i]) {
        while (s[i] != p[i]) i++;
        cnt++;
      }
    }
    cout << cnt << endl;
  }
}
