Welcome to the Q&A Forum

Redirecting images to a page is not a common practice, also this will result in weird situations.

For example: 
An user searches your product on images.google.com and would like to show the original image. This will cause a redirect to your product page instead of the image.

Redirect images to images if you would like to have the images of the "new" website indexed by Google instead of the old ones. You could check Google Webmaster Tools and Google Analytics whether Google is responding to your signals.

You can also take a look at the Change of Address functionality in Google Webmaster Tools which allows you to update the Google index of SiteABC to SiteXYZ for next 180 days. After that period Google will probably know the new situation.

You could protect the /test/ directory with a username / password by using .htpasswd.
This will prevent Google crawling your site and saves you your Crawl Budget. Make sure you don't link to the test/protected pages.

You can remove the /test/ from Google by requesting a removal in Google Webmaster Tools. Otherwise there is a possibility that users visit some pages in the /test/ dir and receive a 404 error when you finished the tweaks.