from collections import deque
T=int(input())
for _ in range(T):
    N=int(input())
    X=[]
    Xs=set()
    Y=[]
    for _ in range(N):
        x,y=input().split()
        X.append(x)
        Y.append(y)
    done=0
    Q=deque([("a",[])])
    while Q:
        s,conv=Q.popleft()
        for i,x in enumerate(X):
            if x in s:
                for j in range(len(s)-len(x)+1):
                    if x==s[j:j+len(x)]:
                        if i not in conv:
                            Q.append((s[:j]+Y[i]+s[j+len(x):],conv+[i]))
                        else:
                            done=1
                    if done:break
            if done:break
        if done:break
    print("Yes" if done else "No")