#include <bits/stdc++.h>
using namespace std;
int main() {
  int t, n, arr[103];
  cin >> t;
  while (t--) {
    int ans = 1;
    cin >> n;
    for (int i = 0; i < n; i++) {
      cin >> arr[i];
    }
    sort(arr, arr + n);
    for (int i = 0; i < n - 1; i++) {
      if (arr[i + 1] == arr[i] + 1) {
        ans = 2;
      }
    }
    cout << ans << endl;
  }
}
