#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];
    int c = 0;
    sort(a, a + n);
    for (int i = 0; i < n - 1; i++)
      if (a[i] == a[i + 1] - 1) c++;
    if (c != 0)
      cout << 2 << endl;
    else
      cout << 1 << endl;
  }
  return 0;
}
