9465_스티커_DP

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class _9465_스티커_DP {
	public static void main(String args[]) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int t = Integer.valueOf(br.readLine());
		while (t-- > 0) {
			int n = Integer.valueOf(br.readLine());
			long[][] a = new long[n + 1][2];
			{
				String[] line = br.readLine().split(" ");
				for (int i = 1; i <= n; i++) {
					a[i][0] = Long.valueOf(line[i - 1]);
				}
			}
			{
				String[] line = br.readLine().split(" ");
				for (int i = 1; i <= n; i++) {
					a[i][1] = Long.valueOf(line[i - 1]);
				}
			}
			long[][] d = new long[n + 1][3];
			for (int i = 1; i <= n; i++) {
				d[i][0] = Math.max(d[i - 1][0],
						Math.max(d[i - 1][1], d[i - 1][2]));
				d[i][1] = Math.max(d[i - 1][0], d[i - 1][2]) + a[i][0];
				d[i][2] = Math.max(d[i - 1][0], d[i - 1][1]) + a[i][1];
			}
			long ans = 0;
			ans = Math.max(d[n][0], Math.max(d[n][1], d[n][2]));
			System.out.println(ans);
		}
	}
}