https://www.acmicpc.net/problem/9465
T=int(input())
for _ in range(T):
n=int(input())
mlist=[list(map(int, input().split())) for _ in range(2)]
dp=[[0]*n for _ in range(2)]
dp[0][0]=mlist[0][0]
dp[1][0]=mlist[1][0]
for i in range(1, n):
if i==1:
dp[0][i]=dp[1][i-1]+mlist[0][i]
dp[1][i]=dp[0][i-1]+mlist[1][i]
else:
dp[0][i]=mlist[0][i]+max(dp[1][i-1], dp[1][i-2])
dp[1][i]=mlist[1][i]+max(dp[0][i-1], dp[0][i-2])
print(max(dp[0][n-1], dp[1][n-1]))