/*************************************************
Author :supermaker
Created Time :2016/3/25 19:19:54
File Location :C:\Users\abcd\Desktop\TheEternalPoet
**************************************************/
#pragma comment(linker, "/STACK:102400000,102400000")
#include <set>
#include <bitset>
#include <list>
#include <map>
#include <stack>
#include <queue>
#include <deque>
#include <string>
#include <vector>
#include <ios>
#include <iostream>
#include <fstream>
#include <sstream>
#include <iomanip>
#include <algorithm>
#include <utility>
#include <complex>
#include <numeric>
#include <functional>
#include <cmath>
#include <ctime>
#include <climits>
#include <cstdarg>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cctype>
#include <cassert>
using namespace std;
#define CFF freopen ("aaa.txt", "r", stdin)
#define CPPFF ifstream cin ("aaa.txt")
#define DB(ccc) cout << #ccc << " = " << ccc << endl
#define PB push_back
#define MP(A, B) make_pair(A, B)
typedef long long LL;
typedef unsigned long long ULL;
typedef double DB;
typedef pair <int, int> PII;
typedef pair <int, bool> PIB;
const int INF = 0x7F7F7F7F;
const int MOD = 1e9 + 7;
const double EPS = 1e-10;
const double PI = 2 * acos (0.0);
const int maxn = 1000 + 66;
struct Node
{
int v, id, nxt;
};
int head[maxn], edgelen;
Node edge[maxn];
int ind[maxn], oud[maxn], par[maxn], ssta[maxn], top, n;
char ss[maxn][maxn];
bool vis[maxn], used[maxn];
void Init ()
{
memset (head, -1, sizeof (head));
memset (edge, -1, sizeof (edge));
edgelen = 0;
}
void AddEdge (int u, int v, int id)
{
edge[edgelen].v = v;
edge[edgelen].id = id;
edge[edgelen].nxt = head[u];
head[u] = edgelen++;
int tt = head[u];
while (edge[tt].nxt != -1)
{
if (strcmp (ss[edge[tt].id], ss[edge[edge[tt].nxt].id]) > 0)
{
swap (edge[tt].v, edge[edge[tt].nxt].v);
swap (edge[tt].id, edge[edge[tt].nxt].id);
}
tt = edge[tt].nxt;
}
}
int UnFind (int val)
{
if (par[val] == val) return val;
return par[val] = UnFind (par[val]);
}
void dfs (int u, int e)
{
vis[e] = true;
for (int i = head[u]; i != -1; i = edge[i].nxt)
if (!vis[i])
dfs (edge[i].v, i);
ssta[top++] = e;
}
void output ()
{
top--;
printf ("%s", ss[edge[ssta[--top]].id]);
while (top > 0)
printf (".%s", ss[edge[ssta[--top]].id]);
puts ("");
}
void SS ()
{
int cntin = 0, cntout = 0, tt;
bool is_valid = true, is_first = true;
for (int i = 0; i < 26; i++)
if (used[i])
{
if (is_first)
{
is_first = false;
tt = UnFind (i);
}
else
{
if (tt != UnFind (i))
{
is_valid = false;
break;
}
}
}
if (!is_valid)
{
puts ("***");
return ;
}
for (int i = 0; i < 26; i++)
if (used[i])
{
if (ind[i] == oud[i]) continue ;
else if (ind[i] != oud[i] && abs (ind[i] - oud[i]) >= 2)
{
is_valid = false;
break;
}
else if (ind[i] != oud[i] && ind[i] - oud[i] == 1)
cntin++;
else if (ind[i] != oud[i] && oud[i] - ind[i] == 1)
cntout++;
}
if (!is_valid) puts ("***");
else
{
if ((cntin == 0 && cntout == 0) || (cntin == 1 && cntout == 1))
{
int sta = -1;
if (cntin == 0)
{
for (int i = 0; i < 26; i++)
if (used[i])
{
sta = i;
break;
}
}
else
{
for (int i = 0; i < 26; i++)
if (used[i] && (oud[i] - ind[i]) == 1)
{
sta = i;
break;
}
}
top = 0;
dfs (sta, edgelen);
output ();
}
else puts ("***");
}
}
int main()
{
//CFF;
//CPPFF;
int t;
scanf ("%d", &t);
while (t--)
{
scanf ("%d", &n);
Init ();
memset (ind, 0, sizeof (ind));
memset (oud, 0, sizeof (oud));
memset (used, false, sizeof (used));
for (int i = 0; i < maxn; i++)
par[i] = i;
for (int i = 1; i <= n; i++)
{
scanf ("%s", ss[i]);
int len = strlen (ss[i]);
int u = ss[i][0] - 'a', v = ss[i][len-1] - 'a';
AddEdge (u, v, i);
used[u] = used[v] = true;
ind[v]++, oud[u]++;
if (UnFind (u) != UnFind (v))
par[UnFind(v)] = UnFind (u);
}
memset (vis, false, sizeof (vis));
SS ();
}
return 0;
}