t=int(input())
for i in range(t):
n=int(input())
a=input()
a1=a.split()
for i in range(n): a1[i]=int(a1[i])
a1.sort()
b=1 for i in range(1,n):
if a1[i]-a1[i-1]==1:
b=2
break
print(b)
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define IO ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
const long long MOD = 1e9 , OO = 1e18;
const double PI = acos(-1);
const int N = 1e5 + 5;
void solve()
{
int n,ok = 0;
cin >> n;
int a[n];
for (int i = 0 ;i < n ;i++) cin >> a[i];
sort (a,a+n);
for(int i = 0; i< n - 1;i++){
if (a[i+1] - a[i] == 1) ok = 1;
}
if (ok) cout << "2\n";
else cout << "1\n";
return;
}
int main()
{
IO
ll t = 1;
cin >> t;
while (t--)
{
solve();
}
return 0;
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