#include <bits/stdc++.h>
using namespace std;
int main() {
  int t;
  cin >> t;
  while (t--) {
    int n, i, c = 0;
    cin >> n;
    int a[n + 4];
    for (i = 0; i < n; i++) {
      cin >> a[i];
    }
    sort(a, a + n);
    for (i = 0; i < n - 1; i++) {
      if (a[i + 1] - a[i] == 1) {
        c++;
      }
    }
    if (c >= 1) {
      cout << "2" << endl;
    }
    if (c == 0) {
      cout << "1" << endl;
    }
  }
  return 0;
}
