https to URI redirect

The easiest way would be to do something like the following, and then apply it to your VS.

when HTTP_REQUEST {
  if {[HTTP::uri] equals "/"} {
    HTTP::redirect "https://abcd.com/test1app"
  }
}

Keep in mind that there are probably multiple ways to access the root of the site in addition to

/

, like

/index.php

and

default.aspx

. Often you'll want to cover those options as well.