#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("-Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,sse4.2,popcnt,abm,mmx,avx2,tune=native")
#pragma GCC optimize("-ffast-math")
#pragma GCC optimize("-funroll-loops")
#pragma GCC optimize("-funroll-all-loops,-fpeel-loops,-funswitch-loops")
#define IO ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
const long long MOD = 1e9 + 7, OO = 1e18;
const double PI = acos(-1);
const int N = 1e4 + 5;
const int dx[4] = {0, 0, 1, -1};
const int dy[4] = {1, -1, 0, 0};

long long t, n, x, freq[N];

int main()
{
    IO
    cin >> t;
    while (t--)
    {
        for (int i = 1; i < N; i++)freq[i] = 0;
        cin >> n;
        for (int i = 1; i <= n; i++)
        {
            cin >> x;
            freq[x]++;
        }
        long long mx = -OO;
        for (int i = 1; i < N - 1; i++)
        {
            mx = max(mx, freq[i] + freq[i + 1]);
        }
        cout << mx << '\n';
    }
    return 0;
}