import sys
sys.setrecursionlimit(10 ** 6)


def dfs(s: str, used, items):
    for i, (x, y) in enumerate(items):
        p = s.find(x)
        if p == -1: continue
        if used[i]:
            return True

        used[i] = True
        t = s[:p] + y + s[p+len(x):]
        if dfs(t, used, items):
            return True
        used[i] = False

    return False


def solve():
    N = int(input())
    items = []
    for _ in range(N):
        X, Y = input().split()
        items.append((X, Y))

    used = [False] * N
    return dfs('a', used, items)


T = int(input())
for _ in range(T):
    ans = solve()
    if ans:
        print('Yes')
    else:
        print('No')