#include <bits/stdc++.h>
using namespace std;
int maxCount(int n,int a[])
{
    map<int,int> freq;

    for(int i=0; i<n; ++i)
    {
        if(freq[a[i]])
            freq[a[i]] += 1;
        else
            freq[a[i]] = 1;
    }
    int ans = 0, key;

    map<int,int>:: iterator it=freq.begin();

    while(it!=freq.end())
    {
        key = it->first;

        ++it;

        if(freq[key+1]!=0)
            ans=max(ans,freq[key]+freq[key+1]);

    }

    return ans;
}

int main()
{
    int t;
    cin>>t;
    while(t--)
    {
        int n;
        cin>>n;
        int a[10005];
        for(int i=0; i<n; i++)
        {
            cin>>a[i];
        }
        cout<<maxCount(n,a)<<endl;
    }
    return 0;
}