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