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