#include <bits/stdc++.h>
using namespace std;
long long int mod;
void prime(int a, vector<int>& v) {
  for (long long int i = 2; i * i <= a; i++) {
    if (a % i == 0) v.push_back(i);
    while (a % i == 0) {
      a = a / i;
    }
  }
  if (a > 1) v.push_back(a);
}
bool isprime(int a) {
  for (int i = 2; i * i <= a; i++)
    if (a % i == 0) return false;
  return true;
}
long long int expmod(long long int a, long long int b) {
  if (b == 1) return a;
  if (b == 0) return 1;
  long long int m1 = expmod(a, b / 2) % mod;
  if (b % 2) return ((m1 * m1) % mod * a % mod) % mod;
  return (m1 * m1) % mod;
}
long long int gcd(long long int a, long long int b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
long long int lcm(long long int a, long long int b) {
  return (a * b) / gcd(a, b);
}
struct myComp {
  constexpr bool operator()(pair<int, pair<int, int>> const& a,
                            pair<int, pair<int, int>> const& b) const noexcept {
    if (a.first < b.first) return true;
    if (a.first > b.first) return false;
    return a.second.first > b.second.first;
  }
};
int main() {
  int w;
  cin >> w;
  while (w--) {
    int n;
    cin >> n;
    string s;
    cin >> s;
    vector<int> v, u;
    int c = 0, d = 0;
    for (int i = 0; i < n; i++) {
      if (s[i] == '0') {
        if (c > 0) v.push_back(c);
        c = 0;
        d++;
      } else {
        if (d > 0) u.push_back(d);
        d = 0;
        c++;
      }
    }
    if (d > 0) u.push_back(d);
    if (c > 0) v.push_back(c);
    int ans1 = 0, ans2 = 0;
    for (int i = 0; i < v.size(); i++) ans1 += v[i] - 1;
    for (int i = 0; i < u.size(); i++) ans2 += u[i] - 1;
    cout << max(ans1, ans2) << endl;
  }
}
