public static void main(String[] args) {

// TODO Auto-generated method stub

Scanner sc = new Scanner(System.in);

int t = sc.nextInt();

int[][] arr;

int[][] dp;

String[] str;

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

int n = sc.nextInt();

arr = new int[n+1][2];

dp = new int[n+1][2];

for (int j = 0; j < 2; i++) {

for (int k = 1; k <=n; j++) {

arr[j][k] = sc.nextInt();

}

}

dp[1][0] = arr[1][0];

dp[1][1] = arr[1][1];

for(int k=2; k<=n; k++){

dp[k][0] = Math.max(dp[k-1][1],dp[k-2][1] ) + arr[k][0];

dp[k][1] = Math.max(dp[k-1][0],dp[k-2][0] ) + arr[k][1];

}

System.out.println(Math.max(dp[n][0], dp[n][1]));

}

}