package quki.algorithm.dp;

import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStreamReader;

/**

* ½ºÆ¼Ä¿ ¹®Á¦

*

* @author quki

*

*/

public class BOJ9465 {

public static void main(String[] args) throws IOException{

BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

int T = Integer.parseInt(br.readLine());

while(T-- > 0){

int N = Integer.parseInt(br.readLine());

int a[][] = new int[3][100001];

int d[][] = new int[3][100001];

String line1[] = br.readLine().split(" ");

String line2[] = br.readLine().split(" ");

for(int i = 1; i<=2;i++){

for(int j = 1; j<=N;j++){

if(i == 1)

a[i][j] = Integer.parseInt(line1[j-1]);

if(i==2)

a[i][j] = Integer.parseInt(line2[j-1]);

}

}

d[1][1] = a[1][1];

d[2][1] = a[2][1];

for(int i =2; i<=N;i++){

d[0][i] = Math.max(d[1][i-1], d[2][i-1]);

d[1][i] = Math.max(d[0][i-1], d[2][i-1]) +a[1][i];

d[2][i] = Math.max(d[0][i-1], d[1][i-1]) +a[2][i];

}

int ans = 0;

for(int i = 0; i<3; i++){

ans = Math.max(ans, d[i][N]);

}

System.out.println(ans);

}

}

}