#include<bits/stdc++.h>
using namespace std;
const int maxn = 1e3 + 10;
struct EDGE{ int v, nxt, id; bool used; }Edge[maxn<<2];
int Head[30], cnt, N;
int IN[30], OUT[30];
int St;
int ans[maxn<<2], len;
string str[maxn];inline void init()
{memset(Head, -1, sizeof(Head));memset(IN, 0, sizeof(IN));memset(OUT, 0, sizeof(OUT));cnt = 0;St = 0x3f3f3f3f;
}inline void AddEdge(int From, int To, int ID)
{Edge[cnt].used = false;Edge[cnt].id = ID;Edge[cnt].v = To;Edge[cnt].nxt = Head[From];Head[From] = cnt++;
}void DFS(int v, int id)///由于是要边路径而不是顶点路径，所以要带个边参数
{for(int i=Head[v]; i!=-1; i=Edge[i].nxt){if(!Edge[i].used){Edge[i].used = true;int Eiv = Edge[i].v;DFS(Eiv, Edge[i].id);}}if(id != -1)ans[len++] = id;//    for(int i=Head[v]; i!=-1; i=Edge[i].nxt){///如果不像代边的编号参数，可以这样写
//        if(!Edge[i].used){                   ///也可以达到记录边路径的作用
//            Edge[i].used = true;
//            DFS(Edge[i].v);
//            ans[len++] = Edge[i].id;
//        }
//    }
}int main(void)
{int nCase;scanf("%d", &nCase);while(nCase--){init();scanf("%d", &N);for(int i=0; i<N; i++)cin>>str[i];sort(str, str+N);for(int i=N-1; i>=0; i--){///将边从大的到小的插入，因为是链式向前星存储int Len = str[i].length();int From = str[i][0] - 'a';int To = str[i][Len-1] - 'a';AddEdge(From, To, i);IN[To]++, OUT[From]++;St = min(To, min(St, From));///记录一下DFS的起点，对应了有欧拉回路的情况
        }int Not_equal, St_num, Des_num;Not_equal = St_num = Des_num = 0;for(int i=0; i<26; i++){if(!IN[i] && !OUT[i]) continue;if(IN[i] != OUT[i]) Not_equal++;if(OUT[i] - IN[i] == 1){St_num++;St = i;///此时已经可以判定没有欧拉回路了，改变起点，将出度多的作为起点}else if(IN[i] - OUT[i] == 1)Des_num++;}if(Not_equal > 0){///如果有点的出入度不想等if(!(Not_equal == 2 && St_num == 1 && Des_num == 1)){///并没有欧拉路径puts("***");continue;}}len = 0;DFS(St, -1);///恢复欧拉路径if(len != N){puts("***");continue;}for(int i=len-1; i>=0; i--){if(ans[i] == -1) continue;cout<<str[ans[i]];if(i > 0) putchar('.');else puts("");}}return 0;
}
/*
2
6
aloha
arachnid
dog
gopher
rat
tiger
3
oak
maple
elm
*/