#include <bits/stdc++.h>
using namespace std;
int main() {
  int t, n, a[1000], d;
  cin >> t;
  while (t--) {
    cin >> n;
    for (int i = 0; i < n; i++) {
      cin >> a[i];
    }
    sort(a, a + n);
    d = 0;
    for (int i = 1; i < n; i++) {
      if (a[i] - a[i - 1] <= 1) {
        d++;
      }
    }
    if (d)
      cout << 2 << endl;
    else
      cout << 1 << endl;
  }
  return 0;
}
