#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int q;
  cin >> q;
  while (q--) {
    int n;
    cin >> n;
    int a[n];
    for (int i = 0; i < n; i++) cin >> a[i];
    sort(a, a + n);
    int count = 0;
    for (int i = 1; i < n; i++) {
      if (a[i] - a[i - 1] == 1) count++;
    }
    if (count)
      cout << 2;
    else
      cout << 1;
    cout << endl;
  }
  return 0;
}
