#include <bits/stdc++.h>

 using namespace std;

 const int maxn = ;

 int dp[maxn][],a[][maxn],n;

 int main(){

     int kase;

     scanf("%d",&kase);

     while(kase--){

         scanf("%d",&n);

         for(int i = ; i <= n; ++i)

             scanf("%d",&a[][i]);

         for(int i = ; i <= n; ++i)

             scanf("%d",&a[][i]);

         memset(dp,,sizeof dp);

         for(int i = ; i <= n; ++i){

             dp[i][] = max(dp[i-][],max(dp[i-][],dp[i-][]));

             dp[i][] = max(dp[i-][],dp[i-][]) + a[][i];

             dp[i][] = max(dp[i-][],dp[i-][]) + a[][i];

         }

         printf("%d\n",max(max(dp[n][],dp[n][]),dp[n][]));

     }

     return ;

 }

 /*

 2

 5

 50 10 100 20 40

 30 50 70 10 60

 7

 10 30 10 50 100 20 40

 20 40 30 50 60 20 80

 */