CSS how to define the distance of a div from the bottom of a page, not the bottom of the window?

I have a page that does not fit inside the browser window so the user has to scroll to the bottom. I want to make a div that is 50vh from the bottom, but if I do this:

    .test{ 
       position: absolute;
       bottom: 50vh;
    }

Then it just makes it so that when the page loads it is 50vh from the bottom of the window, not 50vh from the bottom of the entire page, which extends past the window. How would I make a div that is 50vh from the bottom of the entire page? Thanks.