#include <stdio.h>
#include <stdlib.h>

int max(int a, int b) {
    return a>b ? a:b;
}

int main() {
    int T;
    scanf("%d",&T);

    while(T--) {
        int n;
        scanf("%d",&n);
        int** sticker = (int**)malloc(sizeof(int*)*2);
        int** dp = (int**)malloc(sizeof(int*)*2);
        for(int i=0; i<2; i++) {
            sticker[i] = (int*)malloc(sizeof(int)*n);
            dp[i] = (int*)malloc(sizeof(int)*n);
            for(int j=0; j<n; j++) {
                scanf("%d", &sticker[i][j]);
                dp[i][j] = 0;
            }
        }

        dp[0][0] = sticker[0][0];
        dp[1][0] = sticker[1][0];
        if(n==1) printf("%d\n",max(dp[0][0], dp[1][0]));
        else {
            dp[0][1] = sticker[1][0] + sticker[0][1];
            dp[1][1] = sticker[0][0] + sticker[1][1];

            for(int i=2; i<n; i++) {
                dp[0][i] = sticker[0][i] + max(dp[1][i-1],dp[1][i-2]);
                dp[1][i] = sticker[1][i] + max(dp[0][i-1],dp[0][i-2]);
            }

            printf("%d\n",max(dp[0][n-1],dp[1][n-1]));
                
            for(int i=0; i<2; i++) {
                free(sticker[i]);
                free(dp[i]);
            }
            free(sticker);
            free(dp);
        }
    }

    return 0;
}