Unexpected redirect if upstream server redirect in nginx proxy_pass with URI specified

This is my reverse proxy server block

server {
    listen 80;
    server_name test.com;

    location / {
        proxy_pass http://127.0.0.1:8080;
        proxy_set_header HOST $host;
    }
}

I creates all endpoint in my upstream server without trailing slash, redirecting all trailing slash endpoint to it's non trailing slash endpoint in my upstream server as well, test.com/foo/ will redirect to test.com/foo, everything is fine until I want proxy test.com to http://127.0.0.1:8080/app/, here's the server block

server {
    listen 80;
    server_name test.com;

    location / {
        proxy_pass http://127.0.0.1:8080/app/;
        proxy_set_header HOST $host;
    }
}

And this is what happened:

1. test.com redirect to test.com/app, expect test.com
2. test.com/foo still the same as expected
3. test.com/foo/ redirect to test.com/app/foo, expect test.com/foo

Can't find the solution to this, any help?