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