#pragma GCC optimize "trapv"
#include <bits/stdc++.h>
#define faster ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL)
using namespace std;
#define ll long long
#define ld long double
#define pb push_back
#ifndef ONLINE_JUDGE
#define debug(x) cerr << #x<<" "; _print(x); cerr <<"("<<__LINE__<<")"<<endl;
#else
#define debug(x)
#endif
#define vi vector<int>
#define vll vector<long long>
#define yes cout << "YES" << endl
#define no cout << "NO" << endl
#define mp make_pair
typedef unsigned long long ull;

void _print(ll t) {cerr << t;}
void _print(int t) {cerr << t;}
void _print(string t) {cerr << t;}
void _print(char t) {cerr << t;}
void _print(ld t) {cerr << t;}
void _print(double t) {cerr << t;}
void _print(ull t) {cerr << t;}

template <class T, class V> void _print(pair <T, V> p);
template <class T> void _print(vector <T> v);
template <class T> void _print(set <T> v);
template <class T, class V> void _print(map <T, V> v);
template <class T> void _print(multiset <T> v);
template <class T, class V> void _print(pair <T, V> p) {cerr << "{"; _print(p.ff); cerr << ","; _print(p.ss); cerr << "}";}
template <class T> void _print(vector <T> v) {cerr << "[ "; for (T i : v) {_print(i); cerr << " ";} cerr << "]";}
template <class T> void _print(set <T> v) {cerr << "[ "; for (T i : v) {_print(i); cerr << " ";} cerr << "]";}
template <class T> void _print(multiset <T> v) {cerr << "[ "; for (T i : v) {_print(i); cerr << " ";} cerr << "]";}
template <class T, class V> void _print(map <T, V> v) {cerr << "[ "; for (auto i : v) {_print(i); cerr << " ";} cerr << "]";}

void solve()
{ 
    int n;
    cin>>n;
    vi a(2*n);
    for (int i = 0;i<2*n;i++) cin>>a[i];
    sort(a.begin(),a.end());
    vi b(2*n);
    for (int i = 0 ;i<n;i++) b[2*i] = a[i];
    for (int i = n, j = 1;i<2*n;i++,j+=2) b[j] = a[i];
    for (int i = 0;i<2*n;i++) cout<<b[i]<<" ";
    cout<<endl;
}
signed main()
{
    faster;
#ifndef ONLINE_JUDGE
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
freopen("error.txt","w",stderr);
#endif
    int t;
    cin >> t;
    while (t--)
        solve();
}