import java.io.*;
class trienode
{
trienode a[];
boolean isEnd;
trienode()
{
a=new trienode[10];
isEnd=false;
}
}
class PHONELS_TRIE {
private static trienode root;
PHONELS_TRIE()
{
root=new trienode();
}
public boolean insert(String word)
{
//System.out.println(root);
trienode p=root;
for(int i=0;i<word.length()-1;++i)
{
char c=word.charAt(i);
int index=c-'0';
//System.out.println(index);
if(p.isEnd==true)
return false;
if(p.a[index]==null)
{
trienode t=new trienode();
p.a[index]=t;
p=t;
}
else
{
p=p.a[index];
}
}
p.isEnd=true;
return true;
}
public static void main(String args[]) throws IOException
{
Reader sc=new Reader();
int t=sc.nextInt();
while(t-->0)
{
PHONELS_TRIE obj=new PHONELS_TRIE();
int n=sc.nextInt();
boolean ok=true;
String str[]=new String[n];
sc.readLine();
for(int j=0;j<n;++j)
{
str[j]=sc.readLine();
}
for(int j=0;j<n;j++)
{
if(!obj.insert(str[j]))
{
ok=false;
break;
}
}
System.out.println(ok?"YES":"NO");
}
}
static class Reader
{
final private int BUFFER_SIZE = 1 << 16;
private DataInputStream din;
private byte[] buffer;
private int bufferPointer, bytesRead;
public Reader()
{
din = new DataInputStream(System.in);
buffer = new byte[BUFFER_SIZE];
bufferPointer = bytesRead = 0;
}
public Reader(String file_name) throws IOException
{
din = new DataInputStream(new FileInputStream(file_name));
buffer = new byte[BUFFER_SIZE];
bufferPointer = bytesRead = 0;
}
public String readLine() throws IOException
{
byte[] buf = new byte[64]; // line length
int cnt = 0, c;
while ((c = read()) != -1)
{
if (c == '\n')
break;
buf[cnt++] = (byte) c;
}
return new String(buf, 0, cnt);
}
public int nextInt() throws IOException
{
int ret = 0;
byte c = read();
while (c <= ' ')
c = read();
boolean neg = (c == '-');
if (neg)
c = read();
do
{
ret = ret * 10 + c - '0';
} while ((c = read()) >= '0' && c <= '9');
if (neg)
return -ret;
return ret;
}
public long nextLong() throws IOException
{
long ret = 0;
byte c = read();
while (c <= ' ')
c = read();
boolean neg = (c == '-');
if (neg)
c = read();
do {
ret = ret * 10 + c - '0';
}
while ((c = read()) >= '0' && c <= '9');
if (neg)
return -ret;
return ret;
}
public double nextDouble() throws IOException
{
double ret = 0, div = 1;
byte c = read();
while (c <= ' ')
c = read();
boolean neg = (c == '-');
if (neg)
c = read();
do {
ret = ret * 10 + c - '0';
}
while ((c = read()) >= '0' && c <= '9');
if (c == '.')
{
while ((c = read()) >= '0' && c <= '9')
{
ret += (c - '0') / (div *= 10);
}
}
if (neg)
return -ret;
return ret;
}
private void fillBuffer() throws IOException
{
bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE);
if (bytesRead == -1)
buffer[0] = -1;
}
private byte read() throws IOException
{
if (bufferPointer == bytesRead)
fillBuffer();
return buffer[bufferPointer++];
}
public void close() throws IOException
{
if (din == null)
return;
din.close();
}
}
}